Close #39 PR: Upgrade to traceur 0.0.72..
cleanup #39, bump to tracer 0.0.74, and fix #42
0.14.0
readme tweaks
refacto: one compiler ; one sourceMappingURL

- Remove the extra sourceMappingURL.
- Use the same compiler for all the files.
Merge pull request #48 from douglasduteil/refacto-one-compiler-one-sourceMappingURL

refacto: one compiler ; one sourceMappingURL
only generate source map if there's already one in the pipeline
0.14.1
Merge from upstream.