This is major release that modifies the MERF API in a backward-incompatible way. There are a number of things added to this release. The highlights:
* Added ability to add any fixed effects learner, e.g. gradient boosting, deep learning
* Added ability to add validation set and track validation loss during training process
* Updated code to work with pandas 1.0+
* Added a plotting utility to look at results of training
* Added documentation built using Sphinx
* Added more unit tests for pickling, typing, plotting, etc.
* Small bug fixes
* Moved CI over to GitHub Actions
* Published documentation using GitHub pages
* Moved over to Orbyter 2.0
* Moved to Makefile for builds, CI, linting