Remove necessity for ugly bower_components prefix in config/build.js

[joefiorini]

Use a function that calls path.resolve to figure out the right path. Perhaps at that point we can even look to the bower.json for the main file.

[frankie-loves-jesus]

Rails Assets looks for bower.json too. Unfortunately it requires a lot of manual specification in its equivalent to main.js.

Would be cool if Half Pipe could make all this automatic, ie. only having to specify libs once in bower.json and that's it.

[frankie-loves-jesus]

See #94 for more.

[frankie-loves-jesus]

For those who don't know, Rails Assets as in https://rails-assets.org/.