Add license to all source files
Change for compatibility with libgit 0.18.0
Use different technique to lookup git subtree
Begin handling commandline flags/options

Just dealing with options now, not actually doing anything with the
values.
Get rid of crazy globals usage in tracked.c

Replace with slightly less crazy cast from void pointer; used to pass
varying arguments to function pointer callbacks.
Give up after exceeding date/commit limit

Can specify limiting dates with -A and -C flags respectively.
Can specify limiting commits with
Minor rename/refactor
Make output in columnized format