[DISCUSSION] In 1.2.0, use Spark 2.1 and Hadoop 2.7.2 as default compilation in pom.

[Liang Chen]

Hi Dev

In 1.2, there are many features developing  based on Spark 2.1 and Hadoop
2.7.2, so i propose to use Spark2.1 and Hadoop 2.7.2 as default compilation
in pom.

Please discuss and vote.

Regards
Liang