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
TAJO-1205: Remove possible memory leak in TajoMaster. (jinho)

Closes #265
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-1194