TAJO-937: Should use tajo.util.VersionInfo instead of TajoConstants.TAJO_VERSION. (Mai Hai Thanh via hyunsik)

Closes #131
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-907
Renamed TupleComparatorImpl to BaseTupleComparator.