Add an explicit command line instruction for opening a python session

[iovereem]

Following instructions on the Installation Page.
Trying to install the recommended stable release.
https://pymt.readthedocs.io/en/latest/installation.html
I literally copy the commands as listed in the grey boxes.

After the $ conda install pymt, you tell the user to start a python session.
Perhaps better to add a command line that explicitly shows the command on how to start a python session?

[mdpiper]

Address this in FAQ -- Python vs. IPython vs. Spyder vs. Jupyter Notebook/Lab.