Fix memory leak in pure Python Unpacker.feed() (#284)

fixes #283

Author: methane

msgpack/fallback.py

@@ -289,6 +289,8 @@ def feed(self, next_bytes):
         view = _get_data_from_buffer(next_bytes)
         if (len(self._buffer) - self._buff_i + len(view) > self._max_buffer_size):
             raise BufferFull
+        del self._buffer[:self._buff_i]
+        self._buff_i = 0
         self._buffer += view
 
     def _consume(self):