Add a test for port parsing and types

Partly addressing #442

tests/test-files/good/Ports.elm

@@ -0,0 +1,17 @@
+
+-- incoming
+port userID : String
+port signal : Signal Int
+port tuple : (Float,Bool)
+port array : [Int]
+port record : { x:Float, y:Float }
+
+-- outgoing
+port fortyTwo : Int
+port fortyTwo = 42
+
+port time : Signal Float
+port time = every second
+
+port students : Signal [{name:String, age:Int}]
+port students = constant []