main(): Don't explicitly return 0

C++ implicitly returns 0 at end of main
Game: Start player at center instead of top left corner
Unify stateManager, init procedures and window into pe::engine
Add license to engine.cpp
Add onEvent() virtual method to pe::State.

This is the new method for a State to listen to events.
Move fps calculation to pe::engine
Move key state handling to engine
Engine: Add requestQuit() to allow user defined quits
Add FindSFML.cmake to project

It looks like you need this if the user doesn't have
SFML installed correctly
Add Building section to README.md
Menu: Remove test text

SFML 2.0 removes the default font.
SFML 2.0 RC1 still has it, but if the user uses a later version, the
game won't build
pe::ManagerTemplate: Rename addAsset()/getAsset() to add()/get()
pe::ManagerTemplate::add(): Take name and item by const reference
Remove SoundManager and SoundWrap
Add pe::SoundPlayer
Add project info comment to KeyState.hpp and KeyState.cpp
Update documentation
Merge pe::Map::Tile with pe::Map::Map, and move them out of Map namespace

The extra namespace is unnecessary
pe::EntityManager: Add destructor to delete owned items
Style: Reorder class fields (public, protected, private)