Default port mismatch in simulator quickstart

[mikini]

The quickstart (simulator) instructions in the README.md seems to be out of date. The gl_server listens by default on port 21984;

~/openpixelcontrol$ bin/gl_server -l layouts/freespace.json
Loaded "layouts/freespace.json" as channel 1 (625 shapes)
OPC: Listening on port 21984

While the raver_plaid script tries to connect to 7890:

~/openpixelcontrol$ python/raver_plaid.py
    WARNING: could not connect to 127.0.0.1:7890

Specifying the correct port explicitly on the command line makes stuff work, do either;

python/raver_plaid.py localhost:21984
    connected to localhost:21984

or

~/openpixelcontrol$ bin/gl_server -l layouts/freespace.json -p 7890
Loaded "layouts/freespace.json" as channel 1 (625 shapes)
OPC: Listening on port 7890
OPC: Client connected from 127.0.0.1

Documentation or default ports of the endpoints should be updated.