Changed the icon for the "mark all as read" button.

The eye and eye-closed icon will be probably used for other buttons.
Changed the name of the coffeescript file with the event handler for the "mark entry as read when opening it" event.
The "Mark all as read" button is now fully functional. When the user clicks on it all currently visible entries are marked as read, both visually and in the database.

This has required several changes:

- EntriesController#update now expects an array of entry IDs in the params, instead of a single ID
- EntriesController#update now insn't a RESTful route but a custom named route.
- other small changes
Read entries have a lighter green background.

The green that was being used was too strong.