TokenPathBinder: apply URI decoding to path tokens

Otherwise, the token paths are still in their encoded form, pushing this responsibility to the application.
Merge pull request #250 from davidmc24/feature/decode-path-tokens

TokenPathBinder: apply URI decoding to path tokens
ratpack-thymeleaf: use guice multibinder to allow modules to register dialects (#253)

Includes test coverage and an example of usage in the JavaDocs.