Adding a .gitignore
Merge resumption functionality done

Still some more testing that can be done.
Completed -abort functionality

-abort can now be used to clean up all branches made by the tool. It
will try to leave the repo checked out at a reasonable revision. In
declining levels of preferredness:
* If the repo is currently on a user-made branch, leave it.
* Check out a branch that points at the commit that was provided with
  -base when the tool was started (master) is the default.
* If no such branch exists, try to check out 'master'.
* If no such branch exists, do a detached head checkout of the commit
  that was pointed at by the branch provided with -base.
* If the tool can't determine what was provided to -base, check out any
  user-made branch.

TODO: Read replacement data off disk to create branches. Branches are
still hard-coded to particular test cases.