TAJO-1035: Add default TAJO_PULLSERVER_HEAPSIZE

Closes #148
TAJO-910: Simple query (non-forwarded query) should be supported against partition tables.

Closes #138
TAJO-667: Add math function documentation. (Jongyoung Park via hyunsik)

Closes #153
TAJO-1025: Network disconnection during query processing can cause infinite exceptions. (Jihun Kang via jinho)
TAJO-983: Worker should directly read Intermediate data stored in localhost rather than fetching. (Mai Hai Thanh via hyunsik)
TAJO-1070: BSTIndexScanExec should not seek a negative offset. (jinho)

Closes #159
TAJO-1060: Apply updated hadoop versions to README and BUILDING files. (jinho)

Closes #158
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into block_iteration

Conflicts:
	tajo-core/src/main/java/org/apache/tajo/engine/planner/PlannerUtil.java
	tajo-core/src/main/java/org/apache/tajo/engine/planner/physical/ExternalSortExec.java
	tajo-core/src/main/java/org/apache/tajo/worker/Task.java