generate-upgrade can now take target_dir argument

Previous generate-upgrade required renames in rel/ directory:

    rebar generate
    ...changing code...
    mv rel/<release> rel/<release_prev>
    rebar generate
    rebar generate-upgrade previous_release=<release_prev>

With the proposed changes you can now do the same without moving things:

    rebar generate # default target dir: rel/<release>
    ...changing code...
    rebar generate target_dir=<release_new>
    rebar generate-upgrade target_dir=<release_new> previous_release=<release>
inttest/rgen_1: double the timeout a second time

60s still seems to be too low, as it timed out for at least the R15B01
job of the timeout patch merge:
https://travis-ci.org/rebar/rebar/builds/15051701
https://travis-ci.org/rebar/rebar/jobs/15051703
Clean up rebar.config.script
Merge pull request #198 from tuncer/clean-up-rebar-config-script

Clean up rebar.config.script
Merge pull request #190 from tuncer/quadruple-timeout

inttest/rgen_1: double the timeout a second time
Print a more appropriate message on 'rebar info'

To avoid treating plugins' info/2 functions as commands, we catch calls
to 'rebar info'. Previously (4b8c81fb) we simply printed the help
string, but it's much more informative to print the following:
Command 'info' not understood or not applicable
Fix #187 (rename getopt to rebar_getopt)

While at it, update getopt.erl to git rev 78eda3b.
Fix #187 (rename mustache to rebar_mustache)
Fix #205 (erlydtl:compile/3 returns warnings)

Adapt rebar_erlydtl_compiler to handle warnings emitted by
erlydtl:compile/3.
Document compile_only=true
Remove experimental flags

Remove experimental flag from:
* qc compile_only=true
* eunit compile_only=true
* src/foo.app.src.script
* eunit tests=
erlydtl: add missing clause (Reported-by: goofansu)

erlydtl implemented 'binary' option. Add new clause for {binary, false}.
Merge pull request #183 from EchoTeam/generate-upgrade-and-target-dir

generate-upgrade can now take target_dir argument
Merge pull request #196 from tuncer/rebar-run-info

Print a more appropriate message on 'rebar info'
Merge pull request #191 from tuncer/rename-modules

Fix #187 (rename getopt and mustache)
Fix basho/rebar#388

If the syntax error is in a .hrl file, then the reported error message
is not as useful because it's not clear which .erl file was being
compiled. We can fix that easily by first printing what source file was
being processed. We don't change the actual error message, so this will
still work with your editor of choice for jumping to the right line.

Before
------

Success:
Compiled src/foo.erl

Failure:
include/foo.hrl:10: syntax error [...]

After
-----

Success:
Compiled src/foo.erl

Failure:
Compiling src/foo.erl failed:
include/foo.hrl:10: syntax error [...]
rebar_base_compiler: replace fixed size list with a tuple
Merge pull request #210 from tuncer/erlydtl-warnings

Fix #205 (erlydtl:compile/3 returns warnings)
Merge pull request #214 from tuncer/compile_only

Document compile_only=true
Merge pull request #215 from tuncer/experimental

Remove experimental flags