Adds `call()` method that can be used to call any defined The City endpoint.  This method is merely a "coverall" method that keeps us from having to define every method that The City supports.
Fixes typo.
Corrects call to thecityRequest().
Adds check to ensure that params is set before appending '?'
Merge pull request #3 from ericthelast/feature/add-call-method

Feature/add call method