Add https link for cytominer-eval installation

[FloHu]

In the readme front page the link for the most recent cytominer-eval installation is given as

pip install git+git://github.com/cytomining/cytominer-eval@f7f5b293da54d870e8ba86bacf7dbc874bb79565

However, my company server only allows https access. For such cases the link should be

pip install git+https://github.com/cytomining/cytominer-eval@f7f5b293da54d870e8ba86bacf7dbc874bb79565

Please add this to the readme file and include it also in other similar installation instructions. :)

[gwaybio]

@FloHu - feel free to add them yourself :)