Tag release versions in git

[alanorth]

Thanks for this software! Would it be possible for you to tag release versions in git? I see you already use version 0.0.1 in https://github.com/Molmed/fastq_demux/blob/master/fastq_demux/__init__.py.

We install this software on an HPC cluster and it would be nice if we could have a version to keep things clean and for reproducibility etc. For now we use an identifier pointing to the latest git commit, ie /export/apps/fastq_demux/git-dff5823f but it's kinda unwieldy.