Some work on the Felis celestial
Added black semi-transparent background to the pause menu so it is easier to read
Make debug circles around the player translucent
Added behavior-driven AI system; started integrating this into Felis.
Added looping behavior to Felis to attach him to the player.
Added player health regen
Refactor: Move behavior code from Felis to Actor.

Tweaked some of Felis's wait values.
Fix Felis behaviors
Refactor: Move some of Felis's behavior code into actor base class.
Started collision system and added collision prototype.

Also refactored the math and vector libraries a little and did some more work on Felis.
Added circle/line segment collision test to collision prototype.
Added circle/circle collision test
Fix some minor issues with the circle to circle collision test.
Fix bug where enemy radii were being passed around as strings.
More work on the Felis behavior system.

Fixed bug where text colors were always white.
Fix bug with behavior system where non-looping behaviors could not be restarted.
Finish Felis pounce logic; Felis can now pounce on and damage enemies
Felis will now not target enemies that are invalid (such as off screen enemies)
Make sure player gets points for any kills Felis does
Implemented Serpens celestial
Implemented Sagitta celestial