[bug] Console errors contain a weird path to the component

[kubawolanin]

Hi Marcin,

Thanks for your useful component!
I've noticed a minor bug with reporting errors.

Steps to reproduce:

1. Add the component to your project
2. Don't specify a before or after prop.

Expected result:
Console error with the following text:
---> <ImageCompare> at vue-image-compare.vue

Actual result:
---> <ImageCompare> at /home/marcin/Dokumenty/Projekty/vue-image-compare/src/vue-image-compare.vue

Here's the full excerpt from my console:

[Vue warn]: Invalid prop: type check failed for prop "before". Expected String, got Undefined.

found in

---> <ImageCompare> at /home/marcin/Dokumenty/Projekty/vue-image-compare/src/vue-image-compare.vue
       <ImgSplit> at src/components/report/ImgSplit.vue
         <QTabPane>
           <QTabs>
             <ComparisonModes> at src/components/report/ComparisonModes.vue

I believe it's caused by this line in dist file

__vue_options__.__file = "/home/marcin/Dokumenty/Projekty/vue-image-compare/src/vue-image-compare.vue"

Cheers!