louvain not declared as dependency

[pcm32]

On a fresh installation, I get the following error

>>> from SCCAF import *
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/pmoreno/Development/sccaf.sccaf/SCCAF/__init__.py", line 25, in <module>
    import louvain
ModuleNotFoundError: No module named 'louvain'

[chichaumiau]

This is a problem with SCANPY, we can add as dependency, but not a problem with SCCAF.

[pcm32]

I have added this in #4