Feature: Allow the automatic following of redirects to be turned off.

Currently if EasyHttp makes a request, it'll automatically follow any 302 responses it receives. When using EasyHttp to test a web api it can be usefull to check that it receives a 302 rather than following it.

**Implementation**
EasyHttp uses a HttpWebRequest under the hood, which already has this functionality. The change is to HttpRequest, adding a property "AllowAutoRedirect" with a default value of true (to maintain existing behaviour) which toggles the underlying HttpWebRequest.