Simple file change metrics pulled from vcs repo.

To run tests, execute ./runtests.sh

To run it for real: it's still lacking a true CLI script but there are some constants you can modify down at the bottom of churn/churn.py. Fix those to fit your machine, and kick it off. Then go get coffee. :-)

=== Alternative ===
So, after getting different requirements for metrics, we devised another way to get this data. You can simply install the mercurial extension metrics.py in this repo. To install:
edit your ~/.hgrc file and add this line beneath the [extensions] group (if you don't have such a group, create one:

[extensions]
hgext.metrics = <path_to_this_metrics.py>

Once you've done that, go to the repo in question and type:
hg metrics --help

And you're off to the races. Here's an example:

hg metrics -f foo.json -d "2014-11-03 to 2014-11-04"
This will build you a foo.json full of data for all changes in this repo over this 24 hour period.