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
it can, but  would need to switch off the automatic update of update_at when I do the assignment.  It is 2 lines of code, one before and one after.  But, sure, np.