Enforce stubbing/mocking HTTP calls in test environments

[kaiwren]

requiring 'wrest/test' in test_helper.rb or spec_helper.rb should cause an exception to be thrown when a HTTP call is invoked is any tests being run, forcing the call to be mocked/stubbed

People using Wrest should be able to require 'wrest/test' in test_helper.rb or spec_helper.rb to ensure inadvertent calls to unmocked uris raise exceptions