0.3.7 "Simple Silky Smooth Spaces"

This release is mostly concerned with palette analysis, including with analyze(), exact(), and the new analyzeHueWise(). Palettes are expected to change with analysis, and dithers are expected to change just a little with all of those methods. Now we use the simplest possible color difference comparison: squared Euclidean distance in RGB space. Somehow, this seems to work quite well. Several small palettes that were unusable before are very usable now; DawnBringer's DB8 palette, with just 8 colors (and transparent) is able to dither many images quite well. This is an 8-color image. I think, judging by what testing I have done, the new metric should work well, but if it doesn't, you can subclass PaletteReducer (potentially anonymously) and override the differenceMatch(), differenceAnalyzing(), and/or differenceHW() methods.