Changes in 0.3:
  - Changed version number to be in sync with btce-api library.
  - Use a single BTCEConnection to retrieve all depth and trade history
    from the public API.
  - In the main bot loop, request all API data in one shot before calling
    any trader update handlers.
  - In the hello-world-bot.py sample, use a single BTCEConnection to 
    make trading calls in _attemptBuy and _attemptSell.