vcs: Fix internal server error when trying to get diff from Mercurial for paths that include globbing patterns (Issue #308): - Treat passed-in paths as exact matches, dissallowing any type of globbing/regex/pattern matching. - Added accompanying tests.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.