Refine trailing slash behavior.

[tomchristie]

This proposal does two things:

• Modify the wording of how trailing slashes are treated, in order to allow for resources that (1) have a trailing slash and (2) also have a child resource.
• Changes the example to a more conventional example case. (the existing example with multiple consecutive slashes within the URL did not present a typical real-world case, and is more confusing than helpful.)

Without this change it is impossible to represent the http://api.test.com/common/users/ and http://api.test.com/common/users/groups/ resources as desired, because the absolute path resolution for the groups resource would result in http://api.test.com/common/users//groups/.

If required I could present this pull request without also cleaning up the example to be more conventional, but I think it would be less clear.

[tomchristie]

Refs: #578