Hangouts flow on events show page

PT stories: 
https://www.pivotaltracker.com/story/show/71654160
https://www.pivotaltracker.com/story/show/73873708

UI clean up
extracted styling to sass
added Join Live link on event show page

increased Capybara default timeout for javascript driver

demo: http://yaro.herokuapp.com
By having sass imports in application.css, all the sass gets imported into application.css and then everything gets compiled in one go.  The order can be modified by reordering the imports, while the order of sprockets require tree is unpredictable.  

We should change the scss files tree in accordance with best practices.  Putting all the files in global is not it, but equivalent to what we had before.  To be on the safe side for now, I will extract all css from application.css into a separate file and import it first.