v2.3

This is a minor update with the following changes:

• Renamed maxBitDepth parameter to quality to avoid user confusion (some people were mistakenly passing a value of 8 for this)
• Allocated some large-ish arrays on the heap instead of the stack to accomodate platforms like Emscripten with small default stack sizes

I also split the test code and data into its own repository as part of this release, in order to avoid inflicting hundreds of megabytes of unwanted stuff on everyone who clones the repository. Cloning the repository was never the intended way of using the library, but it is a common workflow and people were doing it anyway, so it had to go. Unfortunately it seems there is no good way to actually remove all that data from the repository's history in git, so in the end I pretty much had to just nuke the whole repository and start over. This may screw over existing users because running git pull in an existing clone of the repository will now probably fail, but I'd rather do that and potentially break some people's builds temporarily, than continue to screw over every future cloner forever. Sorry if this bit you! It should be a one-time thing.