TAJO-1150: Some weird methods in QueryClientImpl should be fixed. (Jongyoung Park via hyunsik)

Closes #223
TAJO-1032: Improve TravisCI scripts to adjust log4j log level. (jinho)

Closes #226
TAJO-1153: Merge off-heap package in block_iteration branch to master branch.

Closes #225
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into index_support