Issue 1:
I'm getting a crash both with latest master and with 0.4.6 after loading CategoricalArrays.jl and calling gc(). You can get the code from the nl/crash branch.

_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_) | Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type "?help" for help.
| | | | | | |/ _` | |
| | |_| | | | (_| | | Version 0.6.0-dev.456 (2016-09-03 13:57 UTC)
_/ |\__'_|_|_|\__'_| | Commit a9140fd* (0 days old master)
|__/ | x86_64-redhat-linux

julia> using CategoricalArrays
INFO: Recompiling stale cache file /home/milan/.julia/lib/v0.6/CategoricalArrays.ji for module CategoricalArrays.
julia> gc()
GC error (probable corruption) :
Allocations: 2519259 (Pool: 2518041; Big: 1218); GC: 2
<?#0x7f85f4112870::<circular reference @-1>>

signal (6): Aborted
while loading no file, in expression starting on line 0
gsignal at /lib64/libc.so.6 (unknown line)
abort at /lib64/libc.so.6 (unknown line)
push_root at /home/milan/Dev/julia/src/gc.c:1478
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
gc_mark_module at /home/milan/Dev/julia/src/gc.c:1218
push_root at /home/milan/Dev/julia/src/gc.c:1429
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1368
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
gc_mark_module at /home/milan/Dev/julia/src/gc.c:1218
push_root at /home/milan/Dev/julia/src/gc.c:1429
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
push_root at /home/milan/Dev/julia/src/gc.c:1466
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
gc_mark_module at /home/milan/Dev/julia/src/gc.c:1218
push_root at /home/milan/Dev/julia/src/gc.c:1429
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
gc_mark_module at /home/milan/Dev/julia/src/gc.c:1218
push_root at /home/milan/Dev/julia/src/gc.c:1429
gc_push_root at /home/milan/Dev/julia/src/gc.c:1189 [inlined]
pre_mark at /home/milan/Dev/julia/src/gc.c:1515
_jl_gc_collect at /home/milan/Dev/julia/src/gc.c:1709 [inlined]
jl_gc_collect at /home/milan/Dev/julia/src/gc.c:1865
gc at ./base.jl:145
unknown function (ip: 0x7f85e315de7f)
jl_call_method_internal at /home/milan/Dev/julia/src/julia_internal.h:189 [inlined]
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:1931
do_call at /home/milan/Dev/julia/src/interpreter.c:66
eval at /home/milan/Dev/julia/src/interpreter.c:205
jl_toplevel_eval_flex at /home/milan/Dev/julia/src/toplevel.c:619 [inlined]
jl_toplevel_eval at /home/milan/Dev/julia/src/toplevel.c:641
jl_toplevel_eval_in_warn at /home/milan/Dev/julia/src/builtins.c:590
eval at ./boot.jl:234
unknown function (ip: 0x7f87f6301cdf)
jl_call_method_internal at /home/milan/Dev/julia/src/julia_internal.h:189 [inlined]
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:1931
eval_user_input at ./REPL.jl:66
unknown function (ip: 0x7f85e3156a06)
jl_call_method_internal at /home/milan/Dev/julia/src/julia_internal.h:189 [inlined]
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:1931
macro expansion at ./REPL.jl:97 [inlined]
#3 at ./event.jl:68
unknown function (ip: 0x7f85e314df2f)
jl_call_method_internal at /home/milan/Dev/julia/src/julia_internal.h:189 [inlined]
jl_apply_generic at /home/milan/Dev/julia/src/gf.c:1931
jl_apply at /home/milan/Dev/julia/src/julia.h:1364 [inlined]
start_task at /home/milan/Dev/julia/src/task.c:259
unknown function (ip: 0xffffffffffffffff)
Allocations: 2519259 (Pool: 2518041; Big: 1218); GC: 2
Aborted (core dumped)

Is this a duplicate of #18299?

Issue 2:
Having recently gone through the updating of several packages for 0.4 and trying out the new doc system, I first have to say, I love it! Much kudos to everyone who put in so much effort to build and make the transition.

As an extension to the wonderful new functionality, I find myself wanting to document the daylight out of my packages, but then find myself in an awkward position when I go to write my package's README. Do I duplicate everything? (tedious) Do I just point users to the help system? (not ideal since it's hard to quickly skim over an entire package's contents).

I find myself wishing there was a quick script I could call on my package that would auto-generate a README from the combined docstrings in my package.

I think this would be a great little piece of functionality that would probably be pretty approachable for anyone interested in giving it a go.

I file the issue here, mainly because I'm not exactly sure where this would live. On the one hand, this could obviously go in a package by itself that package developers would then simply install and use. On the other hand, I could see this being something we include with our batteries for new bare packages, a single generate_docs.jl script that we maybe build into the package manager itself via Pkg.docs(pkg) or something like that. Happy to discuss more and get more concrete, but wanted to get the ball running for now.