Leap Motion Icon support

This allows icons to be pushed for users with the Leap Motion plugged in.

It is a progressive enhancement - behavior for non Leap Motion users almost unchanged.

The construct scaling has been altered, with the icons now showing up at a distance of about 40cm, instead of the 5-7m they were at before.

![screenshot 2014-12-01 23 47 31](https://cloud.githubusercontent.com/assets/407497/5272962/0b3b6238-7a37-11e4-8f23-4b3972052e59.png)

http://leapmotion.github.io/HIRO/

Current direction, looking for feedback.  Not sure if these are blockers or not.
 - Make the buttons less jumpy
 - Add manipulation to the back buttons in construct, and then the HUD
 - Explore improving the shadows below the icons, so that they illustrate depth truly.