Feature/search component

[galbwe]

Addresses #109

Changes

• Added a search string to Home component state and included it in the query parameters in the fetch call to /leads.
• Added a Search component that takes a time limit in milliseconds and an event handler as props. After the time limit expires the event handler is passed an onchange event from a text input.
• Refactored the Header component to accept child props and pass the Search component as a child in Home.js. This was to allow passing setSearch as a prop to the Search component without prop drilling through the Header component.

Notes

• Search currently only accepts single word queries. See Allow multiple search terms in api full text search #95 for backend changes that need to be made. We'll need to revisit the frontend component and make sure the query is escaped and validated.

[clairefields15]

Looks great! I'm not super familiar with debounce so I can't give the most thorough review. One thing you might want to add/consider is some kind of validation of the search value like making it all lowercase, removing special characters, escaping spaces, that kind of thing, but it looks like there is another issue for those things!

[clairefields15]

Nice refactor, I've never seen this done before but it's great not to have to prop drill!