Tweak bower.json settings

Some refinements based on the [bower.json specification](https://github.com/bower/bower.json-spec) and to make it more aligned with the npm [package.json](https://github.com/thoughtbot/bourbon/pull/483).

- Added `description`
- Added `license`
- Added `keywords`
- Added `authors`
- Added `repository `
Looks like this may work after all. The Bower docs use the `git://` protocol there, so I've always used that. Whichever one you want to do then