added spec for Employee service

One thing I'd like feedback on was that my "employees.xml" file was based on copying the Sample Retrieve Response XML listed on this page in the docs:

https://ipp.developer.intuit.com/0010_Intuit_Partner_Platform/0050_Data_Services/0400_QuickBooks_Online/Employee

However, I had to change around the xml name space params to match the existing pattern of expected XML.  I modeled it on the "vendors.xml" file.