"develop" prereqs shouldn't be listed as reverse deps by default

as discovered at http://neilb.org/2013/08/14/total-dependencies.html -- the reverse dependencies list shouldn't list 'develop' requirements as prerequisites (at least not without setting an option that is off by default), as including these dists can be misleading -- when installing a dist from PAUSE, develop prereqs are not required, only configure, runtime and test.
