TAJO-1061: Update build documentation. (jaehwa)

Closes #157
TAJO-1078: Update contributor list.

Closes #165
TAJO-1074: Query calculates wrong progress before subquery init. (jinho)

Closes #162
TAJO-962: Column reference used in LIMIT clause incurs NPE.

Closes #164
TAJO-981: Help command (\?) in tsql takes too long time. (YeonSu Han via jaehwa)

Closes #174
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/master/GlobalEngine.java