cs179New
Projectile Updates

- Updated to click & drag interface with angled shots.
- Added rigid body to enemies and added collision detection and removal
of enemies on hit.
- Updated cannon to disappear as soon as it passes the ground plane.
Merge pull request #1 from achen052/master

Projectile Updates
Implemented Health, Time Based Waves, and the DFS

Health script is attached to each enemy object, it decreases each time
it is hit by an "ammo" tagged object. Waves run at set intervals, but a
new wave will start only when all the enemies have been destroyed at a
given wave. The DFS pathing seems a little weird since it looks like it
takes its time looking for the target position.
Merge branch 'master' of https://github.com/mrome007/cs179ProjectVer1

Conflicts:
	Assets/Prefabs/TowerBasicAmmo.prefab
	Assets/Scripts/Buy_Shoot_Modes.cs
	Assets/Scripts/DestroyOnContact.cs
Updated Tower Projectile

- Added damage to tower projectile and damaging enemies
- Modified flying units to have random spawn height
- Removed flying units when passing tower x position. Fix for it not
always intersecting with the target position
- Updated projectile speed
- Updated projectile to destroy on contact
- Changed slow enemy color
Merge pull request #2 from achen052/master

Updated Tower Projectile