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
https://github.com/rails/sass-rails
```
Sprockets provides some directives that are placed inside of comments called require, require_tree, and require_self. DO NOT USE THEM IN YOUR SASS/SCSS FILES. They are very primitive and do not work well with Sass files. Instead, use Sass's native @import directive which sass-rails has customized to integrate with the conventions of your Rails projects.
```
The main concern is that sprockets first compile the scss file and then include it into application.css, which means that we cannnot use any imports that were made in other scss files and have to import them explicitly, eg. bootstrap is imported in application.css, but in order to use it in hangouts.scss or elsewhere, it has to be imported again, but that would override any cascading rules that we might already have.