Fix header element positions as window is resized

Make the workflow step bar and the title bar maintain their width
and position, even as the window shrinks in width.

Addresses #579
Add orange state to workflow step icons

Addresses #579
Cache bust new workflow step icons

Addresses #579
Remove border around logo image in IE8

IE8 draws borders around linked images.

Addresses #579
Set type of tools menu toggle button

If the button element does not have it's ``type`` attribute set
to ``button``, in IE8 and IE9, pressing Enter will trigger a
button press.  Presumably this is because the default button type
is ``submit``.

Closes #913
Fix box-sizing in IE8 and IE9

Apparently it's just ``box-sizing`` for IE8/IE9, not
``-ms-box-sizing``
Make story summary textarea narrower

Even with fixing box-sizing in IE, there's still some overlap after
entering edit mode in the wysihtml5 editor.  Just make the textarea
95% width instead of 100%. This is hacky, but it still looks fine.
Add a tooltip to the menu toggling icon

Addresses #579
Force showing an updated version of the tour

Change the cookie that marks whether the user has seen the builder
tour, forcing users to see the tour again.  This is because the
changes to the workflow and the new placement of the title and
byline elements, and their editing behaviors, make it likely
that many users will need some reorientation.

Change the name of the cookie from ``storybase_show_builder_tour``
to ``storybase_builder_tour_seen`` and change its value from a
boolean value to a version string.  In the future, if the tour
needs to be updated and shown to users again, simply bump the
version number, stored in the ``TOUR_VERSION`` variable and
the tour will be shown again.

Addresses #579
Show title editor on a failed story validation

If the story is missing a title when the user tries to publish the
story, show the title editor and its tooltip so they know how to
add the title.

Also, when there are only warnings, mention that the story was
published first, then list the missing suggested fields, so there's
no ambiguity about the story being published or not.

Addresses #578
Hide asset type icons for unavailable asset types

When doing usability testing for #578 and #579, a number of users
gave us feedback that it was confusing/annoying to have icons that
weren't clickable.  Hide icons with the ``unavailable`` CSS class.