Added note about HttpException is not thrown by default (#132)

Added note about HttpException is not thrown by default

Author: Nyholm

httplug/exceptions.rst

@@ -17,6 +17,11 @@ TransferException                  something unexpected happened \-
                                                                  ``getResponse()``
 ================================== ============================= ===================
 
+.. note::
+    By default clients will always return a PSR-7 response instead of throwing a ``HttpException``. Write your 
+    application to check the response status or use the :doc:`/plugins/error` to make sure 
+    the ``HttpException`` is thrown.
+
 .. note::
 
     The ``sendAsyncRequest`` should never throw an exception but always return a