depth information

URI：
https://www.bitstar.com/api/v1/market/depth/{businessType}?size={size} （GET）
Parameter description：
businessType：See the first chapter（General parameter specification）
size：the amount of deepth information，not nessary，default 50.
Return value format：

    {   
    	"asks":[    
    	       {"price":<digital cash price>,"amount",<digital cash amount>},    
    	       {"price":<digital cash price>,"amount",<digital cash amount>},    
    	       {"price":<digital cash price>,"amount",<digital cash amount>},    
    	       ...  
    	],  
    	"bids":[    
    	       {"price":<digital cash price>,"amount",<digital cash amount>},    
    	       {"price":<digital cash price>,"amount",<digital cash amount>},    
    	       {"price":<digital cash price>,"amount",<digital cash amount>},    
    	       ...  
    	]   
    }   

additional illustrations：
asks：asks depth，bids：bids depth，order by price desc