Finally performing texture mapping

• `genDestImagePixelBytesAtPosition()` now rounds the texelUVs to the nearest int and uses that to index into the src image’s data, and uses the resultant `nearestTexelSample` as the values put into the byte buffer— now finally performing texture mapping.
	» Currently displays awesome-looking-but-sadly-incorrect circular stripe patterns. Need to figure out what’s wrong.
• Switched `genDestImageBytesAtPosition()` and `genDestImagePixelBytesAtPosition()` to use UInt8 as the byte type instead of char.
	» It’s what CFDataGetBytes() uses and is clearer in meaning.
• `- destImage` now caches the src image’s CGData, width, and height in `_srcData`, `_srcWidth`, and `_srcHeight` ivars for later use by `genDestImagePixelBytesAtPosition()`.
	» `_srcData` manually released in `- dealloc`.