added stock, watch_list, technical_indicator, trading_system
downgraded ruby version from 2.0.0 to 1.9.3 for compatibility with ib-ruby
added required parameter currency to IB::Contract, added readers for symbol & contract
overloaded << operator in watch_list
converted SMA from an instance method to a module method
overloaded << operator in watch_list now accepts arrays and strings
added the ability to fetch historical prices from yahoo finance