Configurable key property for transitions
Configurable key property for transitions

The vue-router component can have a 'key' property which means it's easier to configure transitions between routes with slugs.

With this change in a layout template you can use
```html
<nuxt :routerViewKey="routerViewKey" />
```
And the following for example
```js
    computed: {
      routerViewKey () {
        if (this.$route.name === 'service') {
          return this.$route.name
        } else {
          return this.$route.fullPath
        }
      }
    }
```
This would implement the functionality that @myst729 mentioned here https://github.com/vuejs/vue-router/issues/474 for vue-router - some routes can just switch, but some you may want to transition as though it's a complete new page to an end-user

This is a possible resolution to issue raised here https://github.com/nuxt/nuxt.js/issues/1021
jfroffice/nuxt.js,mgesmundo/nuxt.js,mgesmundo/nuxt.js,jfroffice/nuxt.js