2 kwargs unused in 3 functions - `fca.py`

Two keyword arguments not actually being used in three functions in `fca.py`.

* keyword arguments
  * `supply_index="geoid"`
  * `normalize=False`
* functions
  * `fca_ratio()`
  * `two_stage_fca()`
  * `three_stage_fca()`


see #78
