fix: fragment instance warning

[lionel-bijaoui]

Fix for #45
It seem like a fieldset don't count as a root element for Vue. I added a div and it fix the warning.

[coveralls]

Coverage remained the same at 87.975% when pulling f9915e6 on lionel-bijaoui:LB_fix_fragment_instance into 05fc81c on icebob:master.

[icebob]

Did you test it with a modal?

[lionel-bijaoui]

No, but Vue.js devtools show a warning when a component is a fragment instance. This simple change fix that warning.
I assume it will fix a lot of problem. Fragment instance is a pain to work with in Vue.js.
I hope @blackfyre will test this and give his feedback.

[icebob]

Ok, just I test it before merge.

[icebob]

Merged