Diff syntax highlighting in verbose commits is broken

[akonwi]

After version 5.17.0, the diff grammar in the commit message file is not working.

Steps to reproduce:

1. From the git-plus repo, run git checkout v5.17.0
2. Run apm install in that repo
3. Restart atom if it is already open
4. Open a new git repo in atom
5. Enable verbose commits in the git-plus package settings
6. Try to commit and the diff should be colored.
7. From the git-plus repo, run git checkout v5.17.1
8. Repeat steps 2-5
9. Try to commit and the diff should be all grey.

[akonwi]

This will be fixed in the next update of the package