code: public Traverson startWith(final String uriTemplate, final Map<String, Object> vars) {
          return startWith(fromTemplate(uriTemplate).expand(vars));
      }
docs: Start traversal at the application/hal+json resource idenfied by {@code uri}.
  
  @param uriTemplate the {@code URI} of the initial HAL resource.
  @param vars uri-template variables used to build links.
  @return Traverson initialized with the {@link HalRepresentation} identified by {@code uri}.