Fix windows paths in tests

Turns out we were normalizing the expected error. We need to
normalize the actual error.

Fixes #956
Remove unnecessary pipe operators in Makefile.

Fixes #973

Review URL: https://github.com/google/traceur-compiler/pull/976

Closes #976, closes #973.
HoistVariableTransformer should understand destructuring
Keep binding identifiers in assignment patterns
new System.register for circular deps