Duplicate Parameter Name Detection

[ChrisTalman]

Throw an error if two or more parameter resources share the same name within the scope of an endpoint.

For instance, the following endpoint would throw an error, because two parameter resources share the name item:

/items/:item/:subItem/:item

Currently, the final parameter value in the endpoint would overwrite all other parameter values of the same name, as only one value can exist in the parameters object.