Repaired py5bot and support for hexadecimal and web color notations

The 0.5a0 release was a bad release. I botched the py5bot kernel code in a poorly executed merge, and then didn't do sufficient testing to detect the problem. This release fixes those problems.

I have updated my release process to make sure this doesn't happen again. Also, I will prioritize developing a unit test framework for py5.

There are two other changes in this release:

• Proper support for specifying colors using hexadecimal notation and web color notion. See #26.
• The sketch_portal() method will by default throttle the frame rate to 30 frames per second. Previously the default was for no throttling. This change will improve the experience of users who use this for the first time on mybinder, where a Sketch running at the default Sketch speed of 60 frames per second will look jumpy in the Sketch portal when no throttling is used.