Add multiple assignees to issue board card

What does this MR do?

Modifies the CSS and vue component to render multiple assignees in the issue board card

Are there points in the code the reviewer needs to double check?

Shouldn't be

Why was this MR needed?


Screenshots (if relevant)

Before After (4 Assignees) After (+4 assignees)
Screen_Shot_2017-04-24_at_9.39.27_AM 2017-04-24_14.04.22 2017-04-24_14.04.38

Does this MR meet the acceptance criteria?


What are the relevant issue numbers?