Merge pull request #11 from leaena/heatmap_access

Heatmap functionality
Added functionality to allow divs to be put on top of the youtube player
Added click event to toggle heatmap view on and off.  Also prevented page from reloading on every click event
Added Heatmap button, added class 'heatmap' to heatmap div
Implemented css functionality so that heatmap appears right above video progress bar
Merge pull request #12 from saraloves/append_heatmap

Appended heatmap to youtube player
modified heatmap to show intensity of votes better
svg is appending to correct element again
modified opacity of heatmap svg and gave it a background color