- Add explanatory comment
- Remove dead/unused Android test
- Increase image diff threshold to .05 to accommodate slightly different versions of "PingFang" between different test platforms
Core test uses stubbed "glyph.pbf" without Chinese glyphs
Darwin test relies on locally available "PingFang" font.
Android test relies on locally available "Droid" font. 'expected.png' is NOT correct b/c I haven't figured out how to run unit tests on Android yet.