Use job conf to set the useEnumId flag.
Clean up the code.
Remove unused import.
Add unit test.
Update the constant string for USE_ENUM_ID_CONF_KEY.
Change the log information for USE_ENUM_ID_CONF_KEY to debug level.
Merge pull request #284 from pengfeng/feng_support_enum_id

option to read Thrift enum as Int rather than a String in Pig.