Rudimentary brush and eraser preview circle, needs XOR paint mode, but
no good way to access currently
Brush preview hack wasn't playing nice with selections, so I went and
implemented a system for general tool previews. Still doesn't show over
transparent background though :\
Working 'Color Square' Kinda ugly right now
Forgot to clean up some of the Square code
Added cursor and friendly bounds checking to Square
Added numerical indicators to RGB and HSB sliders
Fixed reset button not affecting labels
Herp, only just now thought to add label to Alpha slider
Removed 1-off inaccuracy at edge of Square
Fixed 'gimbal lock' effect on hue and sat sliders. Closes #48
Quick cleanup, ready for merge of #59
Merge pull request #59 from BurntPizza/dev

Brush and Eraser previews + Color Selection Square