Merge pull request pyserial#342 from mghicho/buffer_size_fixed

Fixed the docstring for the set_buffer_size function.

Author: zsquareplusc

serial/serialwin32.py

@@ -418,7 +418,7 @@ def cd(self):
     def set_buffer_size(self, rx_size=4096, tx_size=None):
         """\
         Recommend a buffer size to the driver (device driver can ignore this
-        value). Must be called before the port is opened.
+        value). Must be called after the port is opened.
         """
         if tx_size is None:
             tx_size = rx_size