Merge branch 'graphx' of github.com:ankurdave/incubator-spark into graphx

docs/graphx-programming-guide.md

...rc/main/scala/org/apache/spark/graphx/EdgeDirection.scala

graphx/src/main/scala/org/apache/spark/graphx/Graph.scala

graphx/src/main/scala/org/apache/spark/graphx/GraphOps.scala

graphx/src/main/scala/org/apache/spark/graphx/Pregel.scala

...c/main/scala/org/apache/spark/graphx/impl/GraphImpl.scala

...ala/org/apache/spark/graphx/lib/ConnectedComponents.scala

...src/main/scala/org/apache/spark/graphx/lib/PageRank.scala

...apache/spark/graphx/lib/StronglyConnectedComponents.scala

...ain/scala/org/apache/spark/graphx/lib/TriangleCount.scala

...rc/test/scala/org/apache/spark/graphx/GraphOpsSuite.scala

.../src/test/scala/org/apache/spark/graphx/PregelSuite.scala

...rg/apache/spark/graphx/lib/ConnectedComponentsSuite.scala