Update QuickBooks/IPP/Service/SalesReceipt.php

added findById function to SalesReceipt Service, since it seems to be supported by IDS : https://ipp.developer.intuit.com/0010_Intuit_Partner_Platform/0050_Data_Services/0400_QuickBooks_Online/SalesReceipt
Merge pull request #1 from aj0y/patch-1

Update QuickBooks/IPP/Service/SalesReceipt.php