Use our git on Travis CI.
Use our git on Travis CI.

This should avoid some of the pain points of having an older git that
Travis CI provides. We already do this with `conda-execute` scripts that
we run. This just ensures that we use our (conda-forge's) `git` even
when we are not running a vanilla script.

conda-forge/conda-forge.github.io,conda-forge/conda-forge.github.io,conda-forge/conda-forge.github.io,conda-forge/conda-forge.github.io