title: Adding scalacheck to specs2+spray-testkit example
body: <p>Trying add scalacheck into the spray-testkit + specs2 example:
  service with following route:</p>
  
  <pre><code>def myRoute = get(
    path("add" / IntNumber / IntNumber) ((a, b) =&gt;
      complete((a+b).toString)
    )
  )
  </code></pre>
  
  <p>and the test spec for it:</p>
  
  <pre><code>  "MyService" should {
      "do calculation" in {
        Get("/add/30/58") ~&gt; myRoute ~&gt; check {
          responseAs[String] === "88"
        }
      }
      "do calculation with scalacheck" in {
        check { (a: Int, b: Int) ⇒
          Get(s"/add/$a/$b") ~&gt; myRoute ~&gt; check {
            responseAs[String] === s"${a+b}"
          }
        }
      }
    }
  </code></pre>
  
  <p>should be pretty simple, but my brain is not allowed to formulate the second test case. i get error like </p>
  
  <pre><code>...MyService.Spec.scala:44: not found: value a"
   check { (a:Int, b:Int)
            ^
  ...MyService.Spec.scala:44: value ? is not a member of (Int, Int)
   check { (a:Int, b:Int) ?
                          ^
  </code></pre>
  
  <p>whats going on here and how to fix?</p>