Fixing the reporting of error locations when they occur on the right-hand-sides of cases branches.  Fixes #245
Several bugs, which together fix #246.  See the comment in the new regression test for details.
resolve cached modules in load loop
these are pretty final now
New check-test op forms: is-not, satisfies-not, is%(eq), is-not%(eq).
Also, added basic test cases for all check-test ops.
Emacs: pyret mode support for new keywords: is-not, satisfies-not
Merge branch 'master' of https://github.com/brownplt/pyret-lang
Merge branch 'master' into special-imports
better names and errors for gdrive imports