Convert gml plugin tests to be async [#231]

plugins/gml/popcorn.gml.unit.js

@@ -1,4 +1,4 @@
-test( "Popcorn GML Plugin", function() {
+asyncTest( "Popcorn GML Plugin", function() {
 
   var popped = Popcorn( "#video" ),
       expects = 8,
@@ -14,8 +14,6 @@ test( "Popcorn GML Plugin", function() {
     }
   }
 
-  stop( 10000 );
-
   ok( "gml" in popped, "gml is a method of the popped instance" );
   plus();