Complete visualization - iteration 3

- omitted erroneous code in scatterplot, per mike's instructions
- ran through all code and commented
- validated css and html
- added dynamic legend for google maps
- changed colors so that boston as a whole is encoded as blue, while the
part (zip) is encoded as brown. i did this because i realized that when
i was looking at the legend, it was real easy for me to get confused as
to understanding what the green colors meant on the scatterplot, the bar
charts, and the timeline.