Specs for git ship abort

@charlierudolph Here is the feature spec for your cr-fixGitShipCommitAbort branch. 

Vim starts in normal mode, where it interprets normal characters as control commands. `dG` deletes everything until the end of the file. `ZZ` saves and quits Vim. This allows me to remote control it by simply piping these characters into the STDIN stream when running Vim. 

Unfortunately this don't seem to work with Open4::popen's built-in STDIN channel, so I have to use a temporary file here to pipe its content into STDIN the old-fashioned way.

This PR goes directly into your branch, so you can merge it directly on GitHub.