Remove Bootstrap 2.3.

Remove Amelia theme.
Remove some inline styles.
Remove unused gems.
Add Bootstrap 3.

I followed
http://www.erikminkel.com/2013/09/01/twitter-bootstrap-3-in-a-rails-4-ap
plication/ because it seemed like the same amount of work as learning
about the gems out there.
Fix navbar for bootstrap 3.
Move overrides from application.css to theme
Fix typo in comment.
Restyle event form.
Static navbar, and tweak footer.
Style tables.
Style show player page.

And remove the “you won’t have to bookmark” well.
Style show verified player page.
Merge branch 'upgrade_bootstrap'