Improve detection of Hadoop taskID

Hadoop 2.5.x introduced a bug where the task attempt is used for the
task id. To cope around this, the code searches first for the task
attempt and only then falls back to the task id.

relates #280

(cherry picked from commit a2084e2a9652c5d956239584184dcb2becf9c99d)
Improve taskId detection in EsOutputFormat

Relates #280

(cherry picked from commit 145ad76e413186c5a2d57c61e2300008e7c847e3)
[DOC] Update requirement information
[SPARK] Add mapping id integration test
[SPARK]Bind Map cast to scala.collection package

relates #237
[SPARK] Change RDD to PairRDD

Refactor the RDD[Map[Key,Doc]] to PairRDD[Key,Doc]
Update the docs as well
Fix #284
[DOC] .set is a method of SparkConf not SparkContext

Fix #279