Add a method to get post type objects from /posts/types(/<type>)
Reformat post URI generation tests for legibility
Fix logical error where defining _path on the prototype had unwanted side-effects

Redefining the template should not permanently break the constructor
Move taxonomy and values up from _path container

Now that we're not leveraging the _path object on the prototype for
setting the path's template value, the nesting of the _path object feels
overly heavy vs the top-level instance properties it originally wrapped.

- Constructor.prototype._path.validators is now prototype._pathValidators
- instance._path.template is now instance._template
- instance._path.values has been changed to instance._path

Tests have been updated to reflect the new behavior
Test users().me() and users().id()