Re-designed lean modal with more flexibility

Since I was using this in my own project, I noticed that leanModal was
missing some controls that I would need to use while building a
photo-viewer. Most of all, it was missing the ability to
programmatically call open and close. I broke up the functionality into
smaller parts and let those things happen. (There is only one commit
because I thought of forking way after … technically this is a
different version)
Renamed to leanModal2

Might as well, this is much, much more than a fork.