Fix dependency versions #10
Description
Could you please set the dependency of webpack-dev-middleware to a specific version. The way it's defined now can break my build on a new install.
Version 1.6.0 for example will not work. There is no way to tell if 1.6.2 will break anything. Semantic versioning is no guarantee (in contrast with something like Elm that enforces it), the semantic difference between 1.6.0 and 1.6.1 proves this.