title: unable to use Mixins in vue with typescript
body: <p>I have a folder structure like this </p>
  
  <pre><code>--Page    
     -group.vue    
  --Services
    -groupMixin.ts
  </code></pre>
  
  <p>script of group.vue</p>
  
  <pre><code>&lt;script lang="ts"&gt;
       import { Vue, Component, Mixins } from 'vue-property-decorator'
  
       import { GroupMixin } from '../../services/groupMixin';
       @Component
       export default class Group extends Mixins(GroupMixin) {
          created () {
            console.log(this.test)
          }
        }
  &lt;/script&gt;
  </code></pre>
  
  <p>code of groupMixin.ts</p>
  
  <pre><code>import { Vue } from 'vue-property-decorator'
  //creating mixins.
  export class GroupMixin extends Vue {
    test: string = 'sss'
  }
  </code></pre>
  
  <p>I am facing two problems here.</p>
  
  <p>First, to import a ts file i used ../../, is there any way to use ./ or @/. Without using lang="ts", i can import a js file like this @/services/...</p>
  
  <p>Second, not able to access the varaible <strong>test</strong> which i declared in groupmixin.ts.</p>