Added explanatory text for cells importing modules.

The cells where we are importing modules at the beginning of the notebook are
now explained at a finer granularity. Almost line by line. This provides a
better background on the purpose of every specific command.
hospital/indicator variables
Merge branch 'datavis' of https://github.com/SUNY-Albany-CCI/bc into datavis
use variables for indicators
changed indicators
changed plot color scheme
improved horizontal bar plot
build site