SPARK-2480: Resolve sbt warnings "NOTE: SPARK_YARN is deprecated, please use -Pyarn flag"

Author: witgo <witgo@qq.com>

Closes #1404 from witgo/run-tests and squashes the following commits:

f703aee [witgo] fix Note: implicit method fromPairDStream is not applicable here because it comes after the application point and it lacks an explicit result type
2944f51 [witgo] Remove "NOTE: SPARK_YARN is deprecated, please use -Pyarn flag"
ef59c70 [witgo] fix Note: implicit method fromPairDStream is not applicable here because it comes after the application point and it lacks an explicit result type
6cefee5 [witgo] Remove "NOTE: SPARK_YARN is deprecated, please use -Pyarn flag"