remove description from page attr_accessible

forgot to remove in prior commit
page title cannot be null

validation in model and in db
simple warning blank page title

- page title field uses required
- warning box for validation errors
fix sign out bug

needed jquery_ujs
form page locator attribute from title
pre tag background is white

changes from grey (bootstrap default)
link to tags functionality in page show

click on tag link, will search for tag or title matching tag