Windows doesn't support bcrypt, swap in bcrypt-nodejs

There are two changes in this request; both are intended to make it easier to get started with generator-angular-fullstack.  

First is explicitly including grunt-karma in the npm dev dependencies.

Second is swapping out bcrypt with bcrypt-json.  The function signature is identical.  Most of us (unfortunate) Windows users can't compile native bcrypt.cc easily.

Thanks much.