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


those are valid points, but this is a very big change that I would not like to introduce together with a simple refactoring PR. Ideally we should bring this up in a WSO dev meeting and ask the members for votes on whether to use CoffeeScript or JavaScript.