Update/fix to rust checker.

Switch to --no-trans per https://github.com/mozilla/rust/issues/3808
Switch source to source-inplace since rustc looks for modules in the
source directory.
Add a pattern for rustc warnings and add a unit test.
Update the rust syntax error unit test.
Merge pull request #314 from capdevc/patch-1

Change rustc invocation to --no-trans