various changes for Bootstrap: renaming if:/else: into ask:/otherwise:
(and pushing that through the AST), making examples: be an alias for
check: (and pushing that through the AST), adding an optional "val"
keyword (and pushing that through the AST), making most functions
available as builtins, and avoiding binops in the grammar
forgot a file
adding lexical support for fraction literals
Merge branch 'repl' into for-bootstrap
changes to keep things running
resolving shadowing mistakes that crept in somehow
the new location comes first; this led to backwards-looking messages
restores List's sort-by, adds some location comparisons in error and a terser way of printing locations (skipping the filename), and uses those to print the list of compilation errors tersely and in sorted order.  Fixes #150.
adding docstrings to all the functions and methods of list.arr
cleaning up some algorithms in list to use mutation in favor of avoiding extra allocations
Merge branch 'new-world' into for-bootstrap
just raise for now to get error exit codes
merge upstream from new-world
fix up merge with upstream
new phase0
move methods over to new srcloc
separate file for bootstrap namespace
Merge branch 'for-bootstrap' of github.com:brownplt/pyret-lang into for-bootstrap

Conflicts:
	src/arr/base/list.arr
initial commit (likely broken) to get initial state for image libs
merge new-world