Live sessions - some minor changes

PT story: https://www.pivotaltracker.com/story/show/74032372
Demo: http://yaro.herokuapp.com/hangouts

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


This update rate is way to much for Heroku and we end up with 
   ```2014-09-12T10:09:15.407139+00:00 heroku[web.1]: Error R14 (Memory quota exceeded)```
   ```2014-09-12T10:09:15.406727+00:00 heroku[web.1]: Process running mem=611M(119.4%) ```