Updated proxy.coffee to not lowercase headers, published compiled js.

- Updated proxy.coffee so that it no longer iterates over headers and
lowercases them. Technically the HTTP spec says it shouldn't matter the
what case headers are in, however twitter api throws errors.
- Added compiled javascript library to github repo so it can be used in
projects without being published to npm. See this comment
http://stackoverflow.com/questions/13645824/can-i-write-npm-package-in-c
offeescript#comment24006164_13646337