Logout button

Hello @tessr, 

Please review the following commits I made in branch 'prezjordan-signout-button'.

8e13b916faab79941f364aecfa7ec3859cc3494e (2013-07-27 16:21:14 -0700)
Logout button

308b10b00314a656bc45c0c2aa59779fcb135166 (2013-07-27 16:21:05 -0700)
Converted button.css to LESS - pluralized


R=@tessr
VISIBLE_CHANGES=Logout button