Instapaper count

MOTIVATION
As you probably know, Instapaper does not show any badge or count of the unread items in your account. It's done on purpose and I'm aware of it, but I prefer to be reminded that I have something pending in order to remember to go read it.

So this plugin adds a button in the toolbar which shows the Instapaper unread item count.

FIRST USE
If you are not logged in to Instapaper, the icon shows an exclamation mark. Click on the button and it will open the Instapaper page so you can log in. After that, it will always be able to retrieve the count (you can close the Instapaper tab whenever you want, the plugin doesn't need it to work).

Comments are welcome.