TAJO-830: Some filter conditions with a SUBQUERY are removed by optimizer. (Hyoungjun Kim via hyunsik)

Closes #12
TAJO-834: Add Travis notification to issues@tajo.a.o and IRC. (hyunsik)
TAJO-699: Create a table using LIKE. (Prafulla T via hyunsik)

Closes #21
TAJO-851: Timestamp type test of TestSQLExpression::testCastFromTable fails in jenkins CI test. (Hyoungjun Kim via hyunsik)

Closes #23
TAJO-842: NULL handling in JDBC. (Hyoungjun Kim via jinho)

Closes #18
TAJO-842: NULL handling in JDBC. (fixed a missing log in CHANGES)
TAJO-846: Clean up the task history in woker. (jinho)

Closes #20
TAJO-793: CLI should be able to exit when single query is failed. (Hyoungjun Kim via jinho)

Closes #25
TAJO-854: Supports INSERT INTO with UNION. (Hyoungjun Kim via jihoon)
TAJO-849: Add Parquet storage to HCatalogStore. (jaehwa)
TAJO-839: If all tables participate in the BROADCAST JOIN, there is some missing data.
Remove unused comment and some debug codes
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-839