*** version 2.4

- Separation of variables into beta/psi fix for continuos quadratic. 
- Added data prep step to each treatment class to avoid internal naming
  convention leaking into other functions
- Added test suite - modularized functions to faciliate coverage
- deprecated 'abs' weight and replaced as 'overlap'

*** version 2.2

- Bug fix to allow for single decision point scenario.

*** version 2.1

- Fixed to allow intercept only models.
- Added ability to allow manual treatment weights to include censoring.
- Modified documentation for new functionality.
- Some minor code clean up.

*** version 2.0

This version is a complete redevelopment of the original implementation to
improve consistency and expand functionality across methods. It is not backwards
compatible with prior versions.