chore(traceur): update to version 0.0.55

Update traceur to 0.0.53

CHANGES:
  * sourceMap property changed to plural `sourceMaps`
  * sourceMap result from compiler is in the property named `generatedSourceMap`
  * update error message for syntax error
@thlorenz if `sourceMap` is defined it logs a warning message and updates `sourceMaps`, what do you think?