set library name per target, requires webpack >= 3.1.0

[manelclos]

Hi, this fixes #15

Starting on webpack 3.1.0, library parameter can be a dictionary, see feature at the very end of https://webpack.js.org/configuration/output/#module-definition-systems

I've updated webpack to version 3 which does not pull in any other dependency

The library name when using a script tag is set to VueTabs, using capitalisation suggested in the webpack example (instead of ‘vuetabs')

Easy testing with docs/index.html and using this code instead of app.js:

<script src="https://unpkg.com/[email protected]/dist/vue.js"></script>
<script src="../dist/index.js"></script>
<script>
var Tabs = VueTabs.Tabs;
var Tab = VueTabs.Tab;
var app = new Vue({
    el: '#app',
    components: {
      Tabs,
      Tab
    }
});
</script>

[sebastiandedeyne]

Thanks!