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.
The way Marketo implements their API, this will eventually be per org. I cannot find anything equivalent to salesforce's web oauth flow on their website, even though they require a different endpoint per setup.