Bower and gruntfile improvements

This PR solves our bower install woes by implementing the change mentioned in cfpb/capital-framework#84. It also includes some gruntfile changes designed to make the build process a bit simpler.

Try it out by pulling down these changes and following the [npm link steps](https://github.com/cfpb/generator-cf#contributing). You should be able to run `grunt build` immediately after the generator finishes and it'll compile everything into the dist directory.

The included demo HTML page we're using makes use of all the CF components so ensure you select all components when running the generator. Otherwise, `grunt build` may complain about a missing Less mixin. Eventually we'll dynamically generate the demo page to only include components selected by the user.