title: list of built-in aggregate and transform primitives
body: <p>First, I LOVE featuretools.  It has made my work so much easier and more efficient. One quick question: I was just looking for a full list of non-custom agg &amp; trans primitives, but couldn't seem to find it. Do I just take the list of methods in the API and substitute lowercase (and underscore between) for capitals? </p>