Add tag library

[natsteinmetz]

Research django / python tag libraries and add to project. Link tag to project model.

[kellim]

Unassigning myself so someone else can take this task as I will not be able to complete it in the near future.

Research:
I suggest taking a look at django-taggit https://github.com/jazzband/django-taggit - it's been around since 2009 and the person who originally started it, Alex Gaynor, is a core Django developer. It seems to be the most popular Django tagging package with over 2000 stars on GitHub and it's updated more than the others with the latest update being this year. It works with Python 3 and Django 1.11 or greater.
The license isn't MIT but looks compatible to me (not a licensing expert) https://github.com/jazzband/django-taggit/blob/master/LICENSE

There's a grid of django tagging packages at https://djangopackages.org/grids/g/tagging/ (note: on this grid, the name of the packages are at the top and the info for each project is below the project name - mentioning this because I found it hard to read at first expecting horizontal info)

Note: I didn't look into python tagging packages that were not Django specific so you may want to investigate that also.