Merge pull request #225 from ash211/patch-3

Add missing space after "Serialized" in StorageLevel

Current code creates outputs like:

scala> res0.getStorageLevel.description
res2: String = Serialized1x Replicated

core/src/main/scala/org/apache/spark/storage/StorageLevel.scala

@@ -101,7 +101,7 @@ class StorageLevel private(
     var result = ""
     result += (if (useDisk) "Disk " else "")
     result += (if (useMemory) "Memory " else "")
-    result += (if (deserialized) "Deserialized " else "Serialized")
+    result += (if (deserialized) "Deserialized " else "Serialized ")
     result += "%sx Replicated".format(replication)
     result
   }