Patient data example update

Aaron and I changed the "Analyzing Patient Data" challenge #2, replacing "Grace Hopper" with other strings relevant to the problem and inverting the order of the assignation to show that we can do this (handy when we need to invert key value pairs). Also, we fixed a typo.
there was something similar done in the R material, that is we 'head-ed' the file so the notebook/markdown document will always be in sync with the data.

I propose we add a <code>! head</code> to an ipython notebook cell and have it dump out the head of the file instead of hard-coding the data.