Cleanup

Fixes comments in BlockBindingTransformer

Fixes FindUnusedImports (it broke due to compiler changes)

Remove unused imports
Manual update to verions 0.0.64 and ignore compat errors

TBR=@arv

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1357

Closes #1357.
0.0.65
fix export default class declaration
Use Compiler API to parse in Loader.
Use Compiler to transform tree
Use Compiler to write() output
Fixup sourceRoot and repl
respond to review