Privly button appears in forms and creates a ZeroBin post

Known issues:
- the button only appears in textareas and editable divs so this means it will appear in Google Translate and any other such contexts witch can be frustrating.
- the positioning of the button is not consistent especially in G+, where if the chat window is re-sized the button loses its position.   
nit: Either maker these inline comments or add a line above comments to visually separate it.