Log Message:
Update to 1.4.0. From the changelog:

- The list of commits included in a mob branch is now truncated to a
  maximum of 5 entries to prevent the need for scrolling up in order to
  see the latest included changes.
- Show more informative error message when `mob <cmd>` is run outside of
  a git repository.
- Add environment variable MOB_TIMER which allows setting a default
  timer duration for `mob start` and `mob timer` commands.
- Add automatic co-author attribution. Mob will collect all committers
  from a WIP branch and add them as co-authors in the final WIP commit.
- added support for preventing `mob start` if there are unpushed commits
- better output if one passes a negative number for the timer