TAJO-1156: Improve the comparison of timestamp and date types. (Jihun Kang via jihoon)

Closes #237
TAJO-1174: remove unnessary codes for blobdatum (DaeMyung Kang via hyunsik)
TAJO-1179: Integration tests in TravisCI are occasionally failed due to log size.

Closes #245
TAJO-1169: Some older version of OpenJDK 1.6 does not get default timezone id. (Jihun Kang via hyunsik)

Closes #239
TAJO-1177: Reduce the use of Sun proprietary API. (Jihun Kang via hyunsik)

Closes #243
TAJO-1172: Remove Trevni storage type and its related classes (DaeMyung Kang via hyunsik)

Closes #244
TAJO-1184: Upgrade netty-buffer to 4.0.24.Final. (jinho)

Closes #248
TAJO-1178: Some error messages for wrong JSON queries are not so much helpful. (Jaewoong Jung via jihoon)
TAJO-1195: Remove unused CachedDNSResolver Class. (DaeMyung Kang via jaehwa)

Closes #253
TAJO-1197: Unit test failed: unable to create new native thread. (jinho)

Closes #255
TAJO-1200: Invalid shuffle data of multiple worker in same server. (jinho)

Closes #259
TAJO-1181: Avro schema URL should support various protocols. (jinho)

Closes #252