Datacompy

- dropping Python 2 support (3.5+ only)
- Add `datacompy[spark]` pip install option (54)
- `strip` spaces in join columns (62)
- new function called `all_mismatch`. This will provide all rows which mismatch back as a dataframe so users can export, query, or analyze if there are a lot of them. (64)
- create MANIFEST.in (66)

Small bug fix for Python 2.7 installations.

Adding in `rel_tol`, `abs_tol`, `show_all_columns`, and `match_rates` for `SparkCompare`

First release to public GitHub!