Fix eslint import resolver in Atom v1.18.0

What does this MR do?

Recent changes to Atom have broken the eslint-plugin-resolve module as it is implemented in our configuration. Essentially, the way it is called now, breaks with some assumptions we made in our webpack.config.js about the process that is evaluating that config file. Since the webpack config is being read by Atom Helper instead of node .bin/webpack we cannot assume process.argv[1] is defined. Also, something is wrong with the require.resolve() syntax we were using to check for the existence of node-zopfli. I needed to fix this as well.

Are there points in the code the reviewer needs to double check?

import statements that use defined aliases (like import ~/Foo) should not throw eslint import/xxx errors.

Screenshots (if relevant)

Before this MR: