Initial implementation of Experience

- Minions now give experience to their killer when they die
- Fixed scaling gold for melee minions
Split exp among champions

When a minion dies, split its experience among all enemy champions in
range.
Move the Visual Studio build folder

- Move the Visual Studio build folder to its own directory to enable
side-by-side mingw and Visual Studio builds
Give turrets basic target prioritization
Merge pull request #70 from Michaelcraighoffman/master

Add experience from minions and basic turret AI