Set focus on first item in drop down (textbox, link, whatever it may be)

Set focus on first item in the drop down for keyboard users, so they can quickly tab to the link/item of their choosing.
https://meta.discourse.org/t/keyboard-shortcuts-wish-list/15952
Update onebox gem
Merge pull request #2714 from techAPJ/patch-3

Update onebox gem
Merge pull request #2713 from cpradio/master

Set focus on first item in drop down (textbox, link, whatever it may be)