Fix compile errors on 2018

• #1: Fix compile error on 2018, contributed by @lyuma

Fix distance biases and add atlas compression option

• Remove bias from the distance function and clamping since there were cases where certain text colors would still make the text turn into quads no matter how little the bias was.
• Add option for compressing the text atlas, this probably shouldn't be used unless you are really trying for a small map with low VRAM usage. It just saves on the order of a hundred or so KB in the final package and a couple of megabytes of VRAM.

Initial release with basic functionality

• First release with basic MSDF text rendering. Merry Christmas! 🎄