Rolch

This release implements a more structured API for model estimation. We introduce the `equation` dictionary, which specifies the model for each distribution parameter. Additionally, we fit intercepts for each distribution parameter per defaul now.

Fixes issues 23, 22 by BerriJ, simon-hirsch.

Much appreciated feedback on the API design by Franz Kiraly.

- Added Gamma Distribution
- Improvements in the testing infrastructure
- Better handling of default values
- Some bugfixes

Some bugfixes

- Improve / fix online model selection based on information criteria BerriJ

- Fix the model selection for LASSO
- Fix the weighted RSS calculation and updating
- Higher setuptools versions

Minor release with major improvement in usability and documentation.

We have added _a lot_ of docstrings and set up the first version of the [documentation](https://simon-hirsch.github.io/rolch/).

No other changes in functionality.