appview/pages: show README files in tree listings
We have README files displayed on the main page of a repository, but we
don't do that on subfolders.
In the previous commit, we returned these from the knotserver in the
RepoTreeResponse. We now need to do something similar to what we do on
the index page on the individual tree pages...
Signed-off-by: Skyler Grey <minion@freshlybakedca.ke>