* Allow user to specify es data types in read_csv and pandas_to_eland
Also, some minor maintenance modifications:
- replaced pandas.util.testing with pandas.testing (required in 1.x)
- updated elasticsearch-py requirements to 7.6+ (to support ML code)
* linting file
* Added example notebooks + pytest for these notebooks1
* Fixed paths
* Fixing link in docs
* Minor update for pandas 0.25.3
* Updates for pandas 0.25.3
* Fixing doc links with pandas 0.25.3 update.
* Reverting overwrite to changes to notebooks.