Add Moon.
Merge branch 'master' into moon
Merge branch 'materials' into moon
Fix after merge.
Merge branch 'materials' into moon
Add tests.
Merge branch 'master' into moon
Add moon to scene like sun, stars, and atmosphere.
Add more tests for moon orientation.
Fix tests after moving moon to the scene.
Add moon rendering tests.
Update CHANGES.md.
Merge branch 'master' into moon
Updates based on review.
Add an option to use the Sun as the only light source on the moon.
Fix test
CHANGES.md tweak
Doc tweaks
Merge branch 'master' into moon
Merge branch 'master' into moon

Conflicts:
	CHANGES.md