chore(testing): Run tests/benchmarks on PyPy3
Merge pull request #345 from rouge8/pypy3

Run tests/benchmarks on PyPy3
Merge pull request #343 from kgriffs/chore

Clean up error classes
chore(CONTRIBUTING): Inline Angular.js commit style guide

Rather than make readers hop somewhere else, inline the commit style
information to make it more convenient and obvious what is expected.