[SPARK-7723] Fix string interpolation in pipeline examples

https://issues.apache.org/jira/browse/SPARK-7723

Author: Saleem Ansari <tuxdna@gmail.com>

Closes #6258 from tuxdna/master and squashes the following commits:

2bb5a42 [Saleem Ansari] Merge branch 'master' into mllib-pipeline
e39db9c [Saleem Ansari] Fix string interpolation in pipeline examples

docs/ml-guide.md

@@ -237,7 +237,7 @@ model2.transform(test.toDF)
   .select("features", "label", "myProbability", "prediction")
   .collect()
   .foreach { case Row(features: Vector, label: Double, prob: Vector, prediction: Double) =>
-    println("($features, $label) -> prob=$prob, prediction=$prediction")
+    println(s"($features, $label) -> prob=$prob, prediction=$prediction")
   }
 
 sc.stop()
@@ -391,7 +391,7 @@ model.transform(test.toDF)
   .select("id", "text", "probability", "prediction")
   .collect()
   .foreach { case Row(id: Long, text: String, prob: Vector, prediction: Double) =>
-    println("($id, $text) --> prob=$prob, prediction=$prediction")
+    println(s"($id, $text) --> prob=$prob, prediction=$prediction")
   }
 
 sc.stop()