Fix path tree walking (can now walk into subtrees)
Add argparse to take files to list at command line
Add option to display modifying commit's hex

Modify table writer to allow for varying number of columns.
Minor refactor (make more obj oriented)
Add mechanism to filter which files we list
Allow hiding hidden files, sorting by author date

Use commit date as default, can pull author date by running git
commandline (portability issues?).
By default, don't inspect files starting with '.'.
Also refactor somewhat.
Deal with merge commits properly

If a merge commit changes affecting a file, check parents of that
commit for changes, to see if the changes came from another commit.
Note: if both branches affect the file, then we say the merge commit is
the changing commit. We don't look get the actual source of the merged
changes. (ie: make sure that the changes were merged cleanly, then check
for the source of those changes)