Put all fetched data state in App.js

[willwull]

Fetched data should be saved as state in App instead, so it isn't unnecessarily fetched again.

For example, if you're scrolling down in Browse Movies and click on a movie, when you go back, the page has to scroll back up to the top, since the data is fetched all over.

This doesn't happen when searching, so take a look at how that is implemented.