New PR for MICE

Frank and I decided that I should resubmit a MICE PR from my account due to time limitations on his side.

This PR supercedes #1757.  It is a substantial overhaul of the code, but still contains all the main elements as designed and implemented by Frank in his GSOC project.

Here are two notebooks that illustrate how it can be used:

http://nbviewer.ipython.org/urls/umich.box.com/shared/static/dkinhqyyz374k37tdwdi.ipynb

http://nbviewer.ipython.org/urls/umich.box.com/shared/static/pt8p8tctkl10t32xo97v.ipynb

Feedback welcome and encouraged.