Make download dropdown style on branches / tags pages consistent

Closed Winnie Hellmann requested to merge winh-download-dropdowns-ee into master

This is the same as

What does this MR do?

Change download dropdowns on branches and tags page to new style.


Page Before After
Branches Screen_Shot_2017-08-09_at_12.25.20 Screen_Shot_2017-08-09_at_12.23.19
Tags Screen_Shot_2017-08-09_at_12.26.08 Screen_Shot_2017-08-09_at_12.23.42

What are the relevant issue numbers?,