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.
Good question. Once upon a time I was using this outside of this function, but I can't remember _why_ I moved it into the constructor. Probably left over from me taking one of my shots in the dark.