pandas append function has been deprecated

[opain]

Hi,

The append function has been deprecated in more recent versions of pandas, leading to an error when running gcsc.

It might be worth adding a conda environment or list of required packages to run gcsc.

For example, this conda .yaml seems to works fine:

name: gcsc
channels:

• bioconda
• conda-forge
• defaults
  dependencies:
• python=3.8
• pandas=1.4.0
• scipy
• numpy