API features
- sell stock
- buy stock
- get your current holdings
- get price of a particular stock
- get price of all stocks (dump)
- see how much money you have
- see whether or not you are in the lead.
- get a trade listing timeline?  <- here, I was thinking about providing 100%
  information 
[ who, buy/sell, amount, what, price ]
- access certain market indexes (overall, top n, etc)?

Market characteristics
- All participants are price takers. Orders execute immediately at the market
  price.
- All price movements are simulated by the server. (affected by other players
  actions)
- Spontaneous price movements do occur, to simulate activity of hidden players,
  but the main focus should be player vs. player interaction. Still have to
  have a significant random component so that one player can't manipulate the
  overall volatility by injecting or withholding liquidity.
- Potential black swan events. Crash one stock, etc. Can make this limitlessly
  complex by adding more events and triggers... simulate algo trades.