Add reduceByKey, groupByKey and refactor shuffle Other changes include 1. Adding unit tests for basic RDD functions and shuffle 2. Add a word count example 3. Change the dependency serialization to handle double loading of SparkR    package 4. Allow partitionBy to operate on any RDDs to create pair-wise RDD.
Add reduceByKey, groupByKey and refactor shuffle
Other changes include
1. Adding unit tests for basic RDD functions and shuffle
2. Add a word count example
3. Change the dependency serialization to handle double loading of SparkR
   package
4. Allow partitionBy to operate on any RDDs to create pair-wise RDD.

rickyHong/sparkR-dist,amplab-extras/SparkR-pkg,EugenePig/SparkR-pkg,nvoron23/SparkR-pkg,rickyHong/sparkR-dist,kimchitsigai/SparkR-pkg,RevolutionAnalytics/SparkR-pkg,Liziyao/SparkR-pkg,EugenePig/SparkR-pkg,kuch4r/SparkR-pkg,7c00/SparkR-pkg,7c00/SparkR-pkg,EDMunplugged/SparkR-pkg,liyuqi/SparkR-pkg,Liziyao/SparkR-pkg,kimchitsigai/SparkR-pkg,xzw0005/SparkR-pkg,xzw0005/SparkR-pkg,RevolutionAnalytics/SparkR-pkg,LeoYao/SparkR-pkg,7c00/SparkR-pkg,Draki/SparkR-pkg,xzw0005/SparkR-pkg,EugenePig/SparkR-pkg,EDMunplugged/SparkR-pkg,EDMunplugged/SparkR-pkg,kuch4r/SparkR-pkg,nvoron23/SparkR-pkg,nvoron23/SparkR-pkg,amplab-extras/SparkR-pkg,nvoron23/SparkR-pkg,liyuqi/SparkR-pkg,rickyHong/sparkR-dist,Draki/SparkR-pkg,xzw0005/SparkR-pkg,kcompher/SparkR-pkg,kuch4r/SparkR-pkg,Liziyao/SparkR-pkg,kcompher/SparkR-pkg,kcompher/SparkR-pkg,kuch4r/SparkR-pkg,amplab-extras/SparkR-pkg,amplab-extras/SparkR-pkg,RevolutionAnalytics/SparkR-pkg,rickyHong/sparkR-dist,liyuqi/SparkR-pkg,liyuqi/SparkR-pkg,kcompher/SparkR-pkg,7c00/SparkR-pkg,Liziyao/SparkR-pkg,LeoYao/SparkR-pkg,kimchitsigai/SparkR-pkg,LeoYao/SparkR-pkg,RevolutionAnalytics/SparkR-pkg,EDMunplugged/SparkR-pkg,Draki/SparkR-pkg,LeoYao/SparkR-pkg