Add a search bar to the main screen of the Jobs Index page

[AlstonLin]

We should use elasticsearch to search companies. This is how we should do it:

• The client will send a request to the server at a search endpoint for all companies as the user types
• Server responds with the JSON data needed to fill the Jobs list (eg. what's currently being shown)
• When the client receives this JSON, it updates the contents of the list and re-renders