Added `grunt-cli` and `bower` as `peerDependencies`.

Added `grunt-cli` and `bower` as `peerDependencies` as [discussed here](https://github.com/yeoman/generator-angular/issues/16).

This should simplify Yeoman installation to just `npm install -g yo`!

Here's a quick way to test directly from my branch:
```
npm install -g https://nodeload.github.com/danielmcormond/yo/tar.gz/peer-dependencies
```