Updated Makefile.
Added Scene class.
Updated .gitignore.
Linking against OpenGL framework.
Added call to glActiveTexture, which fixes some isses with RTT.
Added methods for creating empty Textures.
Added opengl/sdl include chuff.
Renderer now takes a scene object
If the scene has ana ssociated texture then the scene is rendered to its framebuffer, else it is rendered to the back buffer.
Include opengl headers and Scene.
Root now has a Scene object (rather than a vector of SpriteBatches)
Add/Remove from scene methods have been updated to use Scene object
renderFrame now passes Scenes to Renderer.
Added addScene and removeScene methods.
Removed methods and members that are no longer needed (since using a dedicated Scene object)
Changed function call order.
Renamed Rectangle2D to Rectangle.
Updated to use new Rectangle API.;