Avoid style import duplication when extracted (fix #139)

Ensure non-scoped style imports have the same identifier by only
adding style-rewriter query parameters when the style is scoped,
becuase extract-text-webpack-plugin relies on the module
identifier for dedupe.

Author: yyx990803

lib/loader.js

@@ -110,12 +110,12 @@ module.exports = function (content) {
   }
 
   function getRewriter (type, scoped) {
-    var meta = '?id=' + moduleId + '&file=' + fileName
+    var meta = '?id=' + moduleId
     switch (type) {
       case 'template':
         return scoped ? (rewriters.template + meta + '!') : ''
       case 'style':
-        return rewriters.style + meta + (scoped ? '&scoped=true!' : '!')
+        return rewriters.style + (scoped ? meta + '&scoped=true!' : '!')
       default:
         return ''
     }