keyboard controls are no longer visible when there are no next or previous sections. Closes #396
Merge remote-tracking branch 'origin/issue/396-keyboard-controls'
Version 1.2.2.

Bugfix release. Include note to error about upgrading South to 1.0, as
that will use south_migrations directory in preference.
Update bundled CSS for change in 5319257c.
Add merge/delete speaker interface.
Javascript hide/reveal the speaker select box.
Add button to delete speaker to speaker detail page.