Update vue-jsx to use babel 7 preset

[byrney]

• Update the vue.jsx preset to use https://github.com/vuejs/jsx
• Remove the merge-props helper (I think it's included in the above)
• Update babel to a compatible version (beta 41)

This fixes the error in #85 but, I'm not sure what other impact it would have or how to test that the rest of codepan still works.