Toggle button in collapsed Navbar works again.

[brainary]

As isOpen and isCollapsable was changed (to expanded and collapsable) in CollapsableMixin the new props needs to be used to get the collapsed Navbar working again.

I get some graphical glitches on Chrome37/Win7 though, that I'm not smart enough to fix;

• Expanded state shows a scroll bar with 1px scroll space.
• Clicking fast on the toggle button locks it in place, any additional clicks won't expand/collapse the Navbar.

No errors on IE11/Win7

Best way to test is to go to the docs page and contract the window till the Navbar collapses.

[pieterv]

Awesome work!

Ill merge this in and we can look at the additional issues after :)