Revert "Update version number for dev branch"

This reverts commit 08579ffa.

project/SparkBuild.scala

@@ -20,7 +20,7 @@ object SparkBuild extends Build {
 
   def sharedSettings = Defaults.defaultSettings ++ Seq(
     organization := "org.spark-project",
-    version := "0.6.0-SNAPSHOT",
+    version := "0.5.1-SNAPSHOT",
     scalaVersion := "2.9.1",
     scalacOptions := Seq(/*"-deprecation",*/ "-unchecked", "-optimize"), // -deprecation is too noisy due to usage of old Hadoop API, enable it once that's no longer an issue
     unmanagedJars in Compile <<= baseDirectory map { base => (base / "lib" ** "*.jar").classpath },

repl/src/main/scala/spark/repl/SparkILoop.scala

@@ -200,7 +200,7 @@ class SparkILoop(in0: Option[BufferedReader], val out: PrintWriter, val master:
       ____              __  
      / __/__  ___ _____/ /__
     _\ \/ _ \/ _ `/ __/  '_/
-   /___/ .__/\_,_/_/ /_/\_\   version 0.6.0-SNAPSHOT
+   /___/ .__/\_,_/_/ /_/\_\   version 0.5.1-SNAPSHOT
       /_/                  
 """)
     import Properties._