move stream to rabit part, support rabit on yarn

subtree/rabit/yarn/build.sh

@@ -1,4 +1,8 @@
 #!/bin/bash
+if [ -z "$HADOOP_PREFIX" ]; then
+    echo "cannot found $HADOOP_PREFIX in the environment variable, please set it properly"
+    exit 1
+fi
 CPATH=`${HADOOP_PREFIX}/bin/hadoop classpath`
 javac -cp $CPATH -d bin src/org/apache/hadoop/yarn/rabit/*
 jar cf rabit-yarn.jar -C bin .