Using ActiveX XHR object for IE when doing PATCH request

In IE8, HTTP PATCH requests are not allowed with the native XHR object.
(see http://msdn.microsoft.com/en-us/library/ms537505(v=vs.85).aspx#xdomain)

I have modified the logic of getXHR() to include the HTTP verb/method as a parameter.
I have also made the conditional logic of the function a bit easier to reason about,
with the addition of adding this check for method. (other common methods like `DELETE`
and `PUT` are still allowed, only `PATCH` needs special treatment at this point)