Use long integers in order book reconstruction

Align the order book reconstruction with the network protocols that use
long integers for quantity.
Improve BBO events in order book reconstruction

Trigger a BBO event when the first order is added to an order book.

Trigger a BBO event when the last bid (or ask) in an order book is
fully executed or canceled, leaving only asks (or bids).

Trigger a BBO event when the only order in an order book is fully
executed or canceled, leaving an empty order book.
Add stock ticker

It is a simple console application that displays the best bids and
offers (BBOs) and latest trades in the trading system.
Merge pull request #11 from jvirtanen/features/ticker

Add stock ticker