Ignore unnecessary files in bower

It's considered a good practice to ignore any unnecessary files in bower so people aren't forced to download them all (eg. tests, build/deploy scripts, src files, etc.)

I've left the build folder, markdown files (README, CHANGELOG, etc.), and the assets at the root of the directory. This should be everything that a person would need for bower.

https://github.com/bower/bower#defining-a-package