Update `ChiantiPy` version

[epassaro]

The last version of ChiantiPy that works with carsus is 0.8.4.

Since ChiantiPy have only a few dependencies maybe it will work for years... or not.

The following dependencies are required to run ChiantiPy,

Python3 (Python 3 is now required as of version 0.8.0)
Numpy
Scipy
Matplotlib
ipyparallel