Added gravitational logic around some temporary player pieces
add variable to control the framerate
only calculate player and particle mass once
use literal arrays instead of constructor functions
particles shrink in distance (allows zooming out)
dirtyVertices and verticesNeedUpdate aren't required
increase default fps to 60
hard-code mass instead of basing it on size
improve appearance of player pieces
slow initial movement of particles and players
tweak acceleration calculations

Use threejs methods for accel calculation.  clamp max velocity to keep
particles from flying away super fast.
tweak accel formula to make it less realistic and more pleasing :)
give players gravity towards origin
Merge branch 'gravity'

Conflicts:
	src/js/app.js
add player colors