Fix for issue #890

Modified the potential_mentor_count to return the number of mentors in
the project. Also, changed the test and made the result.html to work as
paulproteus has suggested. Should the function be renamed to
get_mentor_count ?
This is a nice simple test now.

Is there a test for `get_language_mentors_count` ? If so, then great. If not, we should make sure to grow a test for it.