Module containing some specialized functions to deal with tags.
This Module follows certain conventions. Stick with them.
More concrete: all functions in this module assume that the tags are
located in the tags field, and separated by commas. An example file
foo.markdown could look like:
author: Philip K. Dick
title: Do androids dream of electric sheep?
tags: future, science fiction, humanoid
The novel is set in a post-apocalyptic near future, where the Earth and
its populations have been damaged greatly by Nuclear...
All the following functions would work with such a format.