data flow example
added ActiveRoute support for flexibility.
Tweak variable name
Add Route#propTypes
Clean up findActiveRoutes

When the URL changes, the Routes object updates the active routes. The
routes tree is searched depth-first for matching routes. Routes may match
based on their path, or their name if they don't specify a path.

Should fix #4
Add shared-root example

This example demonstrates how different leaf routes can be nested
under routes that share the same URL. This means that nested pieces
of UI can share the same base URL, which is something in my tests
Ember doesn't currently allow.
Remove redundant example code

Route path defaults to its name, so when path == name the path may be omitted.