Google Code-in

Your task is to create an option in settings to allow the user to choose to free up valuable screen space.

Steps to reproduce:

1. Download a ZIM file through our app.
2. Scroll down the page.

What you get:

• The ActionBar/Toolbar at the top of the page takes up a lot of potentially valuable space.

What we want:

• An option in settings allowing the user to enable a mode where the Actionbar/Toolbar scrolls out of view when the user scrolls down the page but pops back into view when they start scrolling up again. (Like in the official Wikipedia app or Firefox app)
• When this occurs the notification bar should turn transparent so we can see the content behind it.

How to step-in in development: http://wiki.kiwix.org/wiki/Google_Code-in