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.
I don't see this method on the Lead API.