Fixes positioning of buttons on last page of activity

Most of the rest of [#53812235] and [#49305717].

https://www.pivotaltracker.com/story/show/53812235
https://www.pivotaltracker.com/story/show/49305717
Fixes pagination buttons to be clickable outside text

Last piece for [#53812235] and [#49305717]. Before, the buttons outside the text were clickable but didn't do anything; now the whole button is clickable. (Also, simplified the HAML a bit.)

https://www.pivotaltracker.com/story/show/53812235
https://www.pivotaltracker.com/story/show/49305717