=htp reduce set of not-encoded characters in FormData marshalling

Port of https://github.com/spray/spray/pull/918

akka-http-tests/src/test/scala/akka/http/FormDataSpec.scala

@@ -0,0 +1,42 @@
+/**
+ * Copyright (C) 2009-2014 Typesafe Inc. <http://www.typesafe.com>
+ */
+
+package akka.http
+
+import scala.concurrent.duration._
+import org.scalatest.{ BeforeAndAfterAll, Matchers, WordSpec }
+import org.scalatest.concurrent.ScalaFutures
+import akka.actor.ActorSystem
+import akka.stream.FlowMaterializer
+import akka.http.unmarshalling.Unmarshal
+import akka.http.marshalling.Marshal
+import akka.http.model._
+
+class FormDataSpec extends WordSpec with Matchers with ScalaFutures with BeforeAndAfterAll {
+  implicit val system = ActorSystem(getClass.getSimpleName)
+  implicit val materializer = FlowMaterializer()
+  import system.dispatcher
+
+  val formData = FormData(Map("surname" -> "Smith", "age" -> "42"))
+
+  "The FormData infrastructure" should {
+    "properly round-trip the fields of www-urlencoded forms" in {
+      Marshal(formData).to[HttpEntity]
+        .flatMap(Unmarshal(_).to[FormData]).futureValue shouldEqual formData
+    }
+
+    "properly marshal www-urlencoded forms containing special chars" in {
+      Marshal(FormData(Map("name" -> "Smith&Wesson"))).to[HttpEntity]
+        .flatMap(Unmarshal(_).to[String]).futureValue shouldEqual "name=Smith%26Wesson"
+
+      Marshal(FormData(Map("name" -> "Smith+Wesson; hopefully!"))).to[HttpEntity]
+        .flatMap(Unmarshal(_).to[String]).futureValue shouldEqual "name=Smith%2BWesson%3B+hopefully%21"
+    }
+  }
+
+  override def afterAll() = {
+    system.shutdown()
+    system.awaitTermination(10.seconds)
+  }
+}