Formulaic is a high-performance implementation of Wilkinson formulas for Python.

It provides:
* high-performance dataframe to model-matrix conversions.
* support for reusing the encoding choices made during conversion of one
  data-set on other datasets.
* extensible formula parsing.
* extensible data input/output plugins, with implementations for:
  * input:
    * pandas.DataFrame
    * pyarrow.Table
  * output:
    * pandas.DataFrame
    * numpy.ndarray
    * scipy.sparse.CSCMatrix
* support for symbolic differentiation of formulas (and hence model matrices).
