Cleanup
Default behavior in getLinesAdded returns 0

Instead of needing to call a separate function to determine if the entry
actually contains added lines, I handle it in place.
Add function for acquiring lines deleted in commit
Cleanup
Add function to determine number of files changed
Use general function for files/added/deleted

This cuts out a chunk of repetitive code and allows me to hit the same
function whether I'm trying to get number of files changed, lines added,
or lines deleted.
Further simplify stats function

There's a chance that this is being too terse, but at the moment I feel
like it's actually more legible, because it's only a single line, and
there's no connecting the value set on the first line with the function
called on the second.
Cleanup