Use pyHMMER to get rid of binary dependency on HMMER

[prihoda]

This is the first step towards enabling pip install anarci.. I'm not sure if any other changes to setup.py will be needed to get there, we would need to try that out.

• Use pyhmmer instead of HMMER https://github.com/althonos/pyhmmer
  • Use pyhmmer instead of HMMER hmmbuild to build the HMM database
  • Use pyhmmer instead of HMMER hmmscan to find hits
• Add unit tests
• Run tests automatically each week, and also on each pull request using Github Actions

This way, ANARCI can be installed using:

pip install -r requirements.txt
python setup.py install

Speed is unaffected, I've observed just a slight increase in duration similar to the one reported here: https://github.com/althonos/pyhmmer#%EF%B8%8F-benchmarks

I'd be happy to hear your thoughts.