Adding "mark as read" button in the entry list.

Previous entry from the button is marked "Read" when the button is pressed.

screen capture:
For mobile 
![selfoss_m](https://f.cloud.github.com/assets/5386691/2260498/964c38a6-9e42-11e3-8fab-38390290aa73.png)

For pc, etc.
![selfoss_w](https://f.cloud.github.com/assets/5386691/2260509/b0d27ed8-9e42-11e3-92fd-b62e4e9b4b99.png)

Regards,
arbk