Move shortest path and PageRank to bagel.examples

bagel/src/main/scala/bagel/ShortestPath.scala → bagel/src/main/scala/bagel/examples/ShortestPath.scala

-package bagel
+package bagel.examples
 
 import spark._
 import spark.SparkContext._
 
 import scala.math.min
 
+import bagel._
 import bagel.Pregel._
 
 object ShortestPath {
@@ -80,6 +81,7 @@ object ShortestPath {
   }
 }
 
+@serializable
 object MinCombiner extends Combiner[SPMessage, Int] {
   def createCombiner(msg: SPMessage): Int =
     msg.value

bagel/src/main/scala/bagel/WikipediaPageRank.scala → bagel/src/main/scala/bagel/examples/WikipediaPageRank.scala

-package bagel
+package bagel.examples
 
 import spark._
 import spark.SparkContext._
 
+import bagel._
 import bagel.Pregel._
 
 import scala.collection.mutable.ArrayBuffer
@@ -75,6 +76,7 @@ object WikipediaPageRank {
   }
 }
 
+@serializable
 object PRCombiner extends Combiner[PRMessage, Double] {
   def createCombiner(msg: PRMessage): Double =
     msg.value
@@ -103,6 +105,7 @@ object PRCombiner extends Combiner[PRMessage, Double] {
   }
 }
 
+@serializable
 object PRNoCombiner extends DefaultCombiner[PRMessage] {
   def compute(numVertices: Long, epsilon: Double)(self: PRVertex, messages: Option[ArrayBuffer[PRMessage]], superstep: Int): (PRVertex, Iterable[PRMessage]) =
     PRCombiner.compute(numVertices, epsilon)(self, messages match {