Rewrote the breadcrumb calculation to be more readable.

Breadcrumb now has a setMaxWidth() method to set the maximum allowed
width which is used to fit the breadcrumbs.

The breadcrumb width is now based on the container width, passed through
setMaxWidth() by the FileList class.

Now using fixed widths for the test crumbs to simulate consistent
widths across browsers which rendering engines might usually yield
different results.