git-deps doesn't seem to handle slashes on branch names correctly

At the company where I work, we use some conventions around branch names, including prefixing feature branches with `feat/` and bugfix branches with `fix/`. When I try to feed one of those into either git-deps and git-explode, the following message is printed: `Couldn't resolve commitish`. I couldn't find any related issue.

Does anyone get the same behavior? I'm using it under Ubuntu 16.04 and Python 3.5.2.

Thanks for the great work! Excited about the possibilities with those new tools and concepts :)

Reproduce the report with branch names using the `feat/` or `fix/` prefixes in both git-deps and git-explode, under the stated Ubuntu and Python versions if available. Trace where each tool resolves the supplied commitish; done means slash-containing branch names resolve instead of printing `Couldn't resolve commitish`.

Written by the indexing model from the issue text.