Github api instead of raw guzzler

I'm submitting this PR before it is complete.  

I'd like to solve https://github.com/Bee-Lab/bowerphp/issues/49

I think the solution is to wrap the app in a try catch block and look for ```Github\Exception\ApiLimitExceedException``` then prompt the user to login then prompt them to re-run the command.  

There's a lot to change to make this work.  This will be one hairy PR when it's done.  

Feedback is appreciated.