Fix intra-day event order in calendar (#13)

src/ics_cal/icshelper.py

@@ -67,4 +67,4 @@ def retrieve_events(self, ics_url, startDatetime, endDatetime, localTZ):
 
                 event_list.append(new_event)
 
-        return event_list
+        return sorted(event_list, key=lambda k: k["startDatetime"])