Report errors from buble

[Karolis Narkevicius]

When compiling in webpack I get:

ERROR in ./app/createRoot.js
Module build failed: Error
    at JSXOpeningElement.transpile (/Users/karolis/Documents/workspace/overview-ui/node_modules/buble/dist/buble.umd.js:2642:15)
    at JSXElement.transpile (/Users/karolis/Documents/workspace/overview-ui/node_modules/buble/dist/buble.umd.js:880:12)
    at JSXElement.transpile (/Users/karolis/Documents/workspace/overview-ui/node_modules/buble/dist/buble.umd.js:2528:30)
    at ReturnStatement.transpile (/Users/karolis/Documents/workspace/overview-ui/node_modules/buble/dist/buble.umd.js:6126:20)

When compiling directly with buble, I get a more detailed error:

---
8  : export default function createRoot (shell, data) {
9  :   const { initialProperty } = data
10 :   const store = createStore()
11 :   const Root = (props) => {
12 :     return <Overview {...props} shell={shell} />
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Mixed JSX attributes ending in spread requires specified objectAssign option with 'Object.assign' or polyfill helper. (12:11)

Would be great to pass these nice errors to webpack somehow.