[EDF] add close method for file closing.

Author: sprenger

neo/rawio/edfrawio.py

@@ -222,3 +222,6 @@ def _rescale_event_timestamp(self, event_timestamps, dtype, event_channel_index)
 
     def _rescale_epoch_duration(self, raw_duration, dtype, event_channel_index):
         return None
+
+    def close(self):
+        self.edf_reader.close()