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


the hash has to built somewhere, either in the view or in the partial - I prefer in the partial, because different views need different hash for the hangout and I want to keep this out of the view to be cleaner.