Add basic connect

Fixes #5 
You are absolutely right about `mongodb` and `bluebird`. These should not be fixed and they are not. For the rest I'm not absolutely sure. Having some fixed versions for non-core modules feels right though. As I don't have a real argument here, I'm absolutely open if you can name me one (I know there are resources which suggest to use flexible minor and patch versions for libraries but I can't see the argument apply completely for non-core dependencies).