Only mark as read items displayed on the page
Update app.css

Thought the example of the CSS for Themes should have an include back to the original app.css
Merge branch 'mark-all-read' of https://github.com/doubleface/miniflux
Merge branch 'master' of https://github.com/chrislemonier/miniflux
Bugfix #91
Add comments in the example theme
Improve mark items as read