Upgrade mocha-webpack
Upgrade mocha-webpack

mocha-webpack 0.2 adds the `--opts` flag that allows us to put the
`mocha-webpack.opts` anywhere we want.

We don’t actually need that option in the boilerplate itself, but other
projects based on it do, so we want to make that option available.

CodingZeal/react-boilerplate,CodingZeal/react-boilerplate