Merge pull request #1 from sbuessing/Planets

Start a planet branch, try a pull request.
Nits
Merge branch 'master' of https://github.com/sbuessing/swif
Rotating galaxy, sort of
Units knock out units.
8 bit explosions
Planet growth and conquering and size-based production.
Centralized constants.
Performance decreasing.
Start moving geometry to Objective C.  Profiler can't handle it, and seems like a possible perf issue. Also curious about interop.
Removed redundant file level comments.
Move some math calculations to Obj-C (really C macros) and force primitive types for constants.
Merge branch 'master' into shawn

Conflicts:
	Swif/CGGeometry+Swif.swift
Update
Switch to sprites for better performance
.
Merge remote-tracking branch 'origin/shawn' into shawn
collision optimization
Simple AI and moving movement to velocity-based and defined in objects.