feat(package): change `webpack` to `peerDependencies`
feat(package): change `webpack` to `peerDependencies`

This enables the app developer to use webpack 2. You can still get

npm WARN aurelia-webpack-plugin@0.1.0 requires a peer of webpack@>=1.12 <3 but none was installed.

but the plugin will not have a local webpack version not matching the apps version.

aurelia/webpack-plugin,aurelia/webpack-plugin,aurelia/webpack-plugin