Added sfml to cmake
Merge branch 'switch_to_sfml' of https://github.com/RocSolidProductions/Space-Shooter into switch_to_sfml
Removed our Vector2 in favor for sfml's Vector2f
Removed SDL2 mixer and uppdated audiomanager to work with sfml.
Changed SDL rect collision handling to sfml rect collision handling.
Uppdated readme
Using SFML for graphics
Merge branch 'switch_to_sfml' of https://github.com/RocSolidProductions/Space-Shooter into switch_to_sfml

Conflicts:
	CMakeLists.txt
	include/AudioManager.h
	src/Game.cpp
Removed all traces of SDL
Merge pull request #24 from RocSolidProductions/switch_to_sfml

Switch to sfml