Allow PR's to repo that local was forked from

[Former user]

Our set up at work is such that each of us on the team have forked repos that are The Companies, and we PR from our branch, on our individual fork, back into the The Company repo.

I love the Stash Command line tool, and would love to be able to use it at work.

[Tim Gossett]

contribution: https://bitbucket.org/atlassian/stash-command-line-tools/pull-request/13

[Seb Ruiz]

@mrgossett 's PR was merged however doesn't fully complete the story of PRs to an upstream repo where the source branch exists in a child repository.

[Brian Pescatore]

relevant PR: https://bitbucket.org/atlassian/stash-command-line-tools/pull-request/17

[Seb Ruiz]

Thanks to @bpescatore for fixing this. I have released version 0.4.0.