Initial commit
Implement basic functionality.
Use git-log instead of git-diff-tree to get diffstats

A single git-log call is much faster than a git-diff-tree for every
commit.

Also improved the format of the result printout, to better match
Git's idioms.
Switch from using recursion to using iteration

Using recursion causes stackoverflow errors when dealing with large
repos. It's also slower.

However, this iteration implementation isn't correct, because
git-log doesn't guarantee to order all parents before the child,
if the child is a merge commit.
Massively simplify the implementation

We simply merge the diffstats from commits presented by git-log.
No longer do we track parents and subtrees.
Improve ability to handle unexpected lines from git-log
Add args parsing and pass unknown args to git-log

Now you can limit commits for churning using git-log's mechanism.
Add rudimentary exception handling when calling git-log
Rename git-churn.py to git-churn
Add README