Pahfinding and Tower Manager

Fully implemented the pathfinding system.

Added a tower manager to handle all towers on the map
Enemy Movement

Added a test enemy and had it following the path created by the level
when the map is loaded.
Bugs:
Enemy can sometimes get stuck at a waypoint
-- Create a method to check if enemy is going to pass the waypoint and
start it moving to the next waypoint if true
Game crashes when enemy reaches end
--have enemy despawn and decrease life of the player when reaching the
end of the map
Testing Pathfinding

Tested pathfinding on longer map and tried tweaking the algorithm
slightly
Waves

Added waves to the game.  The WaveManager class loads the wave
information from a text file.  Every update it updates the current wave
and if it will spawn an enemy when the timer reaches 0.
Attacking

Added targeting and attacking for towers.  Basic game over state
added(game will exit)
Starting Camera System

Started camera system.  Need to create an interface for all game
objects.  Will create new branch and leave this one as a clean working
copy of the game
wrote MainMenuState

wrote MainMenuState, basically a game state that just contains the title
of the game and our names as creators, but also has a button that starts
the game.