Get KISSmetrics to play with require.js

This is a little hacky. KISSmetrics doesn't set up their library to define an AMD module when appropriate. If they did that, they could still maintain their current advice of loading the code first and into the global namespace. Maybe we can get them to tweak their library.

In the meantime, we have one shim module that sets up the necessary global variable. The other shim module is the remote URL for our KISSmetrics library.

/cc @hampelm