Configured for GitHub Releases and Travis CI.

Hey @kylef! As you mentioned a while ago, it's nicer to leave `.js` files out of the repo and have GitHub releases and let Travis CI build archives for us.

I also improved a lot the `Cakefile`. It's much easier now to work with the Extensions: keep them anywhere convenient and run `cake install` to copy the build directory to the right location.

Also added the right dependencies in `package.json`. And configured `.travis.yml`.

Please feel free to be very critical and pedantic for this review. Now that we have no rush to release, let's make things clean :)

Also, do you mind configuring Travis on your side (as the repo belongs to *apiaryio*)? I think it should be *Build only if .travis.yml is present* + *Build on push* + *Build or pull requests* + have a non-null *Concurrent builds* count. Thanks!