Since #659 , there's no longer a need to manipulate PATH or PYTHONPATH as a pip install will correctly place the mintpy package and all executable scripts to be available in the environment.

Additionally, PyPAS and PySolid are available via conda-forge and no longer need to be cloned and manually built/installed.

Draft because I need to do docs yet

Reminders

• Fix #xxxx
• Pass Codacy code review (green)
• Pass Circle CI test (green)
• Make sure that your code follows our style. Use the other functions/files as a basis.
• If modifying functionality, describe changes to function behavior and arguments in a comment below the function declaration.
• If adding new functionality, add a detailed description to the documentation and/or an example.