Live sessions - some minor changes

PT story: https://www.pivotaltracker.com/story/show/74032372

Changes:
- added ajax refresh for events show page
- added ajax refresh for hangouts index page
- flattened UI for hangouts index page
- added duration to hangouts details

Refactoring:
- combined attributes into json hash for hangout button
- extracted events show html into partials


ok maybe its my fault for not noticing it before, but can we avoid using `and`? It has a very strange behaviour in Ruby (behaves quite differently to `&&`) and is difficult to understand. This expression approximately translates to:
~~~ruby
(redirect_to event_path(params[:event_id])) && (return if local_request? && params[:event_id].present?)
~~~
that means, it is always redirects then returns only if the `redirect_to` returns a truthy value and the condition evaluates to true. I don't think this was your intention and it might have introduced subtle bugs