fixing d-dropdown heading overlap (PR #2505)

as discussed here: https://meta.discourse.org/t/small-ui-bug-show-more-overlap-with-reuslt-list-in-search-box/17194

screenshot 2014-07-04 02 20 06

GitHub

You’ve signed the CLA, awesomerobot. Thank you! This pull request is ready for review.

thanks!