Cleaning up.

1) Support remote per project
2) Make it quieter by default. Make "-v" do something.
3) Don't fetch twice when source & target remote are identical
4) Make output formatting consistent
5) Always tidy up temp branch
6) Always delete local feature branch if it exists, always print message about 
how to recover it, handle case where there's no local feature branch
7) Don't delete auth credentials when connection fails
Remove run_and_verify_no_output
Extract run_command and prompt methods
Reassure users that we won't store their password.
Pull out determine_project_name_from_command_line, find_or_prompt_for_pull_request.
Newlines
Extract merging code out of git-pr script. Getting ready for difftool.
Add "git pr list"
diff & difftool
Merge #4 from floatplane: "Version 3"