We should add a call to action to all Steemit pages

We should add a call to action that gets displayed when a person who is not signed into Steem goes to a page on Steemit. 

Something like 

    "Create a Steem about to join the discussion."
I really think that it will lead to more people joining Steem. At the moment, even if somebody comes in to read an article, they have no reason to join.