Updates to Functions

Made changes to the intersection algorithm, which should improve
performance. Made a few changes to other functions.
Function Changes

Updated a few functions. No major changes made.
Complete Image Addition

Added CompleteImage class, which bundles a sprite and texture together.
This is done to make sure that the sprite always has access to its
parent texture. It is also much more convenient than declaring a texture
and sprite.
Sprite Sheet Support

Added support for Sprite Sheets. This functionality will eventually be
bundled into an Animation class based upon sprite sheets rather than
individual images, although the current Animation class will still be
kept and maintained.
Update to Conform to the Latest SFML Release

Updated classes to no longer depend on the default font. Improved
performance drastically with a few other changes (such as adding an
internal sf::Text object to each GUI object). Improved responsiveness
and aesthetic appeal of several of the GUI objects.
Updated Example Code

Updated the example code to include newer functionality.