Initial REST implementation for marketo API

A better overview of the implemented functions can be seen on the branch's [README](https://github.com/usermindinc/node-marketo/tree/ak-first_commit)

This is an initial stab at implementing a marketo library that integration-marketo will work off of. I was not able to find a node library out there that uses the REST API, but will be happy to switch to one if it pops up.
Just so I'm clear, this is stuff that will be global to our app, not per org?