Fixed bug where textures were loading improperly.

We were setting the image's height equal to its width.
Added some test code and a silly button
Added beginning of font-rendering system.

Don't quite have enough code in place to give it a real testing,
but I'm pretty sure that most of the nitty-gritty/annoying font
technicality stuff is out of the way.
Fixed issues with the font code, added test.

The conversion from 8-biti intensity to RGBA had a silly bug in its
main loop, and we were copying the bitmap to the wrong part of
their square in the texture.

All that is fixed, and we render the texture to the screen just to
see how it looks.
Added code to render strings in TTF fonts.