module: no longer rely on `HTMLImports.whenImportsReady`; this means …

…`using` is 'sync' and cannot be used in the main document when the HTMLImports polyfill is in play.

src/module.html

@@ -41,17 +41,9 @@
 
   var modules = {};
 
-  if (window.HTMLImports) {
-    var using = function(depends, task) {
-      HTMLImports.whenImportsReady(function() {
-        withDependencies(task, depends);
-      });
-    };
-  } else {
-    var using = function(depends, task) {
-      withDependencies(task, depends);
-    };
-  }
+  var using = function(depends, task) {
+    withDependencies(task, depends);
+  };
 
   // exports