Use case: I work on some software that needs to accept URNs that may be
improperly formatted and encode them properly. This patch introduces a new
method, `recodeURNPath`, that will break the URN's path into segments and
make sure that each part of it is encoded properly.

Risks: URI.js treats "URN" as a catch-all category for everything that doesn't
look like an HTTP URL. Many of these schemes may or may not follow the URN
syntactical rules.

My local changes created a bug that caused an exception to be thrown during the `normalize` call of
these methods, which then caused later tests to fail because the wrong decoding/encoding function
was being used.

…and URNs.

1. Used more meaningful tags in the documentation.
2. method names with "URN" in them have been camel-cased to use "Urn" instead.
3. A list of resources and a changelog has been added to the README.