TAJO-1096: Update download source documentation (Mai Hai Thanh via jaehwa)

Closes #182
TAJO-1093: DateTimeFormat.to_char() is slower than SimpleDateFormat.format(). (Jihun Kang via hyunsik)

Closes #177
TAJO-1101: Broadcast join with a zero-length file table returns wrong result data.

Closes #184
TAJO-1103: Insert clause of partitioned table loses some FetchImpls. (jinho)

Closes #186
TAJO-1010: Improve multiple DISTINCT aggregation. (Hyoungjun Kim and jaehwa)

Closes #136
TAJO-1097: IllegalArgumentException: RawFileScanner. (Mai Hai Thanh via jinho)

Closes #183
TAJO-1102: Self-join with a partitioned table returns wrong result data.

Closes #189
TAJO-1099: LogicalPlanner::convertDataType causes NPE in some cases.

Closes #185
TAJO-1104: Using asterisk with GROUP BY causes NPE.

Closes #187
TAJO-1021: Remove the member variable Builder from all classes inherited from ProtoObject.

Closes #188
TAJO-1106: Missing session check in getFinishedQuery API. (Yongjun Park via hyunsik)

Closes #190
TAJO-1093: DateTimeFormat.to_char() is slower than SimpleDateFormat.format(). (bug fix)

Closes #194
TAJO-1069: TAJO-1069: Add document to explain High Availability support. (jaehwa)

Closes #180
TAJO-1105: Add thread which detects JVM pauses like HADOOP's. (jinho)

Closes #191
TAJO-1107: Broadcast join on non-leaf node scans only first data file.

Closes #193
TAJO-1110: JAVA_PULLSERVER_HEAP_MAX in bin/tajo should be increased.

Closes #197
Update Apache POM to 15.
Merge pull request #1 from apache/master

update master branch