Un-ignoring `bower.json` so that the `bower.json` file is available when installing from bower.

Many people rely on the `bower.json` being included when installing from bower. The `bower.json` holds a lot of information people rely on when using bower (the version number of the repo, and the `main` property in particular). 

Currently, this file is not available when installing from bower. 

Our use case is that we use this [gulp build tool](https://github.com/ck86/main-bower-files) to compile all vendor dependencies.  It's nice because you allow the repo owner to control the repo's point of entry.

It is a small change and would help the bower community if you were to accept this pull request. Thanks!