Update pipeline graph styles to match mockup

#### What does this MR do?
* Updates CSS for pipeline graph to match mockup 
* Adds JS to dynamically change line widths based on number of builds

#### Screenshots (if relevant)
![Screen_Shot_2016-10-04_at_2.06.24_PM](/uploads/362378ca23e18a3cc59185eafab9f9ac/Screen_Shot_2016-10-04_at_2.06.24_PM.png)

#### What are the relevant issue numbers?
Closes #21604

See merge request !6320