Add tests, docs, cleanup, and a few enhancements

[metinsenturk]

Hi,

First of all, sorry for leaving you without any tests on this package, my bad. The very first thing in the next release is to add tests. There will be updates on the next release. Basically, the plan is the following list.

• [ ] add tests
• [ ] add documentation with few examples of usage.
• [ ] cleanup the code according to make the package compatible with > pandas 1.0.x releases.