Fixing callbacks for Rails 4

Hi, thanks for a great project!  I'm on rails 4 beta / ruby 2 and got: 

wrong number of arguments (2 for 1) from acts_as_archival.rb:67

In http://edgeapi.rubyonrails.org/classes/ActiveSupport/Callbacks.html and source, looks like run_callbacks now only takes the callback name and a block, and handles before/around/after automatically.

Patched and ran the tests - they all pass.

Cheers,
James