Add ord_type, limit order is the only support one by now. Don't forget to run migration task:

    rake migration:set_history_ord_type
different validations for different ord_type
rename Matching::Order to Matching::LimitOrder
rename mock_order helper
market order model
rename LimitOrderBook to OrderBook
handle market order in orderbook
use sum limit instead of guard price to protect market orders
match market order
match incoming limit order with existing market order
best limit price
prevent solitary market order, match market order with market order
prevent solitary market order
refactor constants and orders
honor market order sum limit
refactor method placement in OrderAsk and OrderBid
add locked and origin_locked to orders
lock/unlock account funds using order.locked
submit market order via api
fix number precision of origin volume