parallel simrank

This is the parallel simrank engine pull request, separate from the local simrank and random engine.
indentation and no need { }
```
val newDelta = union.reduceByKey(_ + _)
  .map(k => 
    (k._1, k._2*decay/(outDegreeMap(k._1._1) + outDegreeMap(k._1._2)))
  )
```