Support test cases without input.
Button can say "Run test case" not "Run test cases" if there's only one test case.
Instead of breadcrumbs, just show the exercise's path.  Basic Ruby logo in gray.
Action buttons have no background; up at very top-right.
Title bar is now black on gray.  Action buttons are too, now at the bottom right again, and they show background color around themselves.
Support blue background.
Clean up CSS
Create exercise 1.1.6, which has a test case.
Bug fix: if you ran test cases on an empty program, it would keep looping the tests over and over.
Demo and Solution buttons at the bottom work now.