Vue scoped css only work in nomodule

Steps to reproduce:
Add following code to `vue-cssextract` example
``` html
<style scoped>
.foobar {
  font-family: mono
}
</style>
```
and add `foobar` class to some html element
reason of bug:
the above css is compiled to `.foobar[data-v-xxxxxx]`, however for different target vue generate different hashed id, so only in legacy mode would scoped css work