Optimize size of lzwImageData Buffer

[pixelmatix]

To fix #2 , I increased the size of lzwImageData from 1024 (32x32) to 1280. This is probably too much. This could be decreased by figuring out the maximum theoretical size of a 32x32 GIF frame, or by running a lot of GIFs containing random data through the decoder and looking for a high water mark in the buffer.