Attempting to exclude lines that we can't necessarily hit in tests, added a test, fixed function name

update_profile_background_image has been in endpoints.py twice for a
bit, my bad.

Using update_profile_banner_image for the function name to update
profile banner image (that's what it was called previously)

twython/streaming/api.py

@@ -113,7 +113,7 @@ class TwythonStreamer(object):
 
         response.close()
 
-    def on_success(self, data):
+    def on_success(self, data):  # pragma: no cover
         """Called when data has been successfull received from the stream
 
         Feel free to override this to handle your streaming data how you
@@ -132,7 +132,7 @@ class TwythonStreamer(object):
         elif 'disconnect' in data:
             self.on_disconnect(data.get('disconnect'))
 
-    def on_error(self, status_code, data):
+    def on_error(self, status_code, data):  # pragma: no cover
         """Called when stream returns non-200 status code
 
         Feel free to override this to handle your streaming data how you
@@ -146,7 +146,7 @@ class TwythonStreamer(object):
         """
         return
 
-    def on_delete(self, data):
+    def on_delete(self, data):  # pragma: no cover
         """Called when a deletion notice is received
 
         Feel free to override this to handle your streaming data how you
@@ -159,7 +159,7 @@ class TwythonStreamer(object):
         """
         return
 
-    def on_limit(self, data):
+    def on_limit(self, data):  # pragma: no cover
         """Called when a limit notice is received
 
         Feel free to override this to handle your streaming data how you
@@ -172,7 +172,7 @@ class TwythonStreamer(object):
         """
         return
 
-    def on_disconnect(self, data):
+    def on_disconnect(self, data):  # pragma: no cover
         """Called when a disconnect notice is received
 
         Feel free to override this to handle your streaming data how you
@@ -185,7 +185,7 @@ class TwythonStreamer(object):
         """
         return
 
-    def on_timeout(self):
+    def on_timeout(self):  # pragma: no cover
         """ Called when the request has timed out """
         return