Merge pull request #20 from dib-lab/mem_expose

MRG: expose memory information

remove unnecessary install_requires

update version to 0.5.3

update version in setup.py

downgrade setuptools req again, for conda-forge

update version to 0.5 in setup.py; downgrade setuptools req

update to v0.4.2

provide long_description from README

Merge pull request #11 from dib-lab/lookup_many

add a 'lookup_many' method to PyMPHF objects