v0.5.0

New features:

• Add the cases and Bmatrix environments.
• Add \checkmark and \circledR symbols.

Other changes:

• Run ttfautohint on our fonts, to produce better results at small font sizes.
• Improve the spacing inside fractions.
• Correctly set environments to the ord type.

Infrastructure changes:

• Redo our screenshot tests to use standard selenium images, and add Chrome screenshots.
• Improve our metrics generation pipeline.
• Fix make dist on Macs.