Read options in a way that works even for Webpack 2.2 (vuejs#538)

This was ported from the master branch (Vue 2.x Loader)

Author: cseufert

lib/loader.js

@@ -28,8 +28,8 @@ module.exports = function (content) {
 
   this.cacheable()
   var loaderContext = this
-  var options = this.vue || this.options.vue || {}
   var query = loaderUtils.parseQuery(this.query)
+  var options = Object.assign({}, this.options.vue, this.vue, query)
   var filePath = this.resourcePath
   var fileName = path.basename(filePath)
   var moduleId = '_v-' + hash(filePath)