As it turns out, Jekyll ignores any directory (or file) that begins
with an underscore.
I forked and added a patch with the addition of an "include"
configuration directive in order to overcome this issue. You can see
the fork here:
https://github.com/lukebayes/jekyll/tree/include
I also associated a pull request with a bug, but can't seem to find
the bug at the moment.
Luke