Switch alphabetical pagination to bootstrap 3

* Upgrade gem to latest version
* Add bootstrap 3 flag in config
Switch kaminari pagination to bootstrap 3

* Upgrade kaminari and use kaminari bootstrap theme (change log for
kaminari: https://github.com/amatsuda/kaminari/releases)
Tidy up user index page

* Put filters into a well
* Remove table from well
* Remove “clear” form and button from filter