Catch exception in spec_helper to give user more helpful error message.
Reverted last change, restoring "Listing Treatments" as the top-level
heading for this page (to be consistent with all of the other index
pages, and because the tests for this page expect it).
Fixed the test that has the message "creating new trait should not
tell the user to choose a citation when trait creation fails for some
other reason".
Added test related to editing of treatments.