Uses config API instead of bower.json

This swaps out all the references to `this.cpui.paths` to use `this.generator.get('path')`. We're also setting up a default config so that if any of the keys (or the entire `.yo-rc.json` file is missing), the defaults will get injected instead. 

- [x] If I create anything with an already existing module, it exits as soon as I've named the module. I haven't figured out the cause of this one yet.
Oh, answered my own question. Just store this on the generator in the constructor:

``` javascript
constructor: function() {
  Base.apply(this, arguments)
  this._defaults = this.src.readJSON('../../config.json')
  this._questions = [ ... ]
}
```