Some quick/small, but important changes to Hextris

In order of urgency:
1) Made HTML page responsive. Will look the same in any size window, no zoom/unzoom necessary.
2) Added retina/high res rendering ability for the canvas. Game won't look blurry on retina displays now (some Macbook Pros, most current iDevices).
3) Fixed height of left/right tap areas so doesn't overflow/extend page.
4) Organized files in project.
5) Formatted code/fixed some small issues brought up by JSLint