Auto merge of #555 - puremourning:waitress-print, r=micbou

[READY] Print a message equivalent to that printed by waitress.serve

#282 breaks emacs-ycmd as it parses the standard output to get the port that ycmd is listening on.

While it probably makes sense for emacs-ycmd to specify the port, this is a regression so we re-introduce the output equivalent to [`waitress.serve`](https://github.com/Pylons/waitress/blob/3850e4c09aa9a55dc5c61985981b4ef719d5ebb8/waitress/__init__.py#L13-L14)

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ycmd/wsgi_server.py

@@ -38,6 +38,13 @@ class StoppableWSGIServer( TcpWSGIServer ):
   def Run( self ):
     """Wrapper of TcpWSGIServer run method. It prevents a traceback from
     asyncore."""
+
+    # Message for compatibility with clients who expect the output from
+    # waitress.serve here
+    print( 'serving on http://{0}:{1}'.format(
+      self.effective_host,
+      self.effective_port ) )
+
     try:
       self.run()
     except select.error: