#22903 Fix code snippeds

* move scala and java sources out of paradox sources
* replace relative paths with $code$ and $akka$
* fix broken includes

akka-docs/src/main/scala/docs/stream/MigrationsScala.scala

@@ -0,0 +1,35 @@
+/**
+ * Copyright (C) 2015-2017 Lightbend Inc. <http://www.lightbend.com>
+ */
+package docs.stream
+
+import akka.stream.scaladsl._
+import akka.testkit.AkkaSpec
+
+class MigrationsScala extends AkkaSpec {
+
+  "Examples in migration guide" must {
+    "compile" in {
+      lazy val dontExecuteMe = {
+        //#expand-continually
+        Flow[Int].expand(Iterator.continually(_))
+        //#expand-continually
+        //#expand-state
+        Flow[Int].expand(i => {
+          var state = 0
+          Iterator.continually({
+            state += 1
+            (i, state)
+          })
+        })
+        //#expand-state
+
+        //#async
+        val flow = Flow[Int].map(_ + 1)
+        Source(1 to 10).via(flow.async)
+        //#async
+      }
+    }
+  }
+
+}