Refactor App.js

[App.js](https://github.com/antonio-ramadas/palbum/blob/master/src/App.js) is doing more than it should. It populates the page (search bar and table).

However, whenever there is an update to the list (e.g., a new album is added) the whole component is rendered. As you can guess, there is no need for it.

Also, with a refactor, the logic would no longer be on a single file and its size will most likely be reduced.

I suggest having one component for the search bar, another for the table and App.js simply calls them on the `render`method.