Ballista 0.13.0 Release

[andygrove]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.
I would like to keep the momentum going and create a 0.13.0 release in the next 1-2 months.

Let's use this issue to co-ordinate on what we would like to see in the next release.

Here are the items that I plan working on:

• Review and improve documentation and examples
• Improve the Python bindings, particularly around adding DataFrame support back in
• Write some architecture and design documentation

Describe the solution you'd like

Describe alternatives you've considered

Additional context