[SPARKR-125] Get the iterator of the parent RDD before launching a R worker process in compute() of RRDD/PairwiseRRDD
[SPARKR-108] Implement map-side reduction for reduceByKey().
Merge pull request #88 from hlin09/hlin09

Adds two functions from Spark: distinct() and mapValues().
Merge pull request #89 from sun-rui/SPARKR-108

[SPARKR-108] Implement map-side reduction for reduceByKey().
Merge pull request #87 from sun-rui/SPARKR-125

[SPARKR-125] Get the iterator of the parent RDD before launching a R wor...
Add maximum() and minimum() API to RDD.
use reduce() to implemement max() and min().
Merge pull request #91 from sun-rui/add_max_min

Add maximum() and minimum() API to RDD.
Adds function Filter(), which extracts the elements that satisfy a predicate.