Ipart

* Replace `CDAT` dependency with `netcdf4`.
* Algorithms are made zonally cyclic.
* Minor change in dependency requirements.

* Replace `CDAT` dependency with `netcdf4`.
* Algorithms are made zonally cyclic.

Contained functionalities:
* Perform THR process of IVT data,
* Detect ARs from THR results, and find AR axis.
* Track ARs across time.

Also included peak separation code, which can be toggled on in `river_tracker1.py`. However, this needs further debugging.

Some changes in the workflow, and optional enhanced continent penetrating is to be expected in next version.