Give the focus to the search field when going to the Home section.
It outlines the search field, which makes it more visible. It also makes the keyboard appear on mobile device, which invites the user to type something
It makes it a bit more clear for the user on what to do
Fixes #40
A click on the Home section empties its content, so that the user he finds the same home page as when he started the application.
Fixes #38
Change placeholder text of the search field, to have something more meaningful for the end-user
Empty the search field after the user has selected and displayed an article.
Fixes #37