Adds more documentation

bfxapi/examples/run_backtest.py

@@ -4,6 +4,13 @@ sys.path.append('../')
 
 from bfxapi.websockets.DataServerWebsocket import DataServerWebsocket
 
+'''
+This script requires you to run an instance of the bfx-hf-data-server on 
+port 8899. For more info on how to setup the data-server please visit:
+https://github.com/bitfinexcom/bfx-hf-data-server
+'''
+
+
 ws = DataServerWebsocket(
   symbol='tBTCUSD',
   host='ws://localhost:8899'