Addonindex webpack failure

@darius, what version of node are you using for building the UI? I get the following after npm run build:dev

Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema.
 - configuration.module.rules[0].exclude: The provided value "node_modules" is not an absolute path!
 - configuration.output.path: The provided value "../resources/static" is not an absolute path!

Nevermind, seems like setting webpack version to 2.2.1 fixes it. See http://stackoverflow.com/questions/42940050/configuration-output-path-the-provided-value-public-is-not-an-absolute-path

I haven’t dig deeper what causes it.

Created a PR at https://github.com/openmrs/openmrs-contrib-addonindex/pull/7

I noticed this broke when I made a commit yesterday, but hadn’t had time to look into it. Thanks @raff for fixing it and saving me the trouble!