Upgrade to Webpack 2

[ChristopherBiscardi]

Removes webpack configurator in favor of regular object access. I think configurator was nice in some respects but overall didn't add enough to be worth rewriting to ensure webpack 2.0 compat.

Shore up the graphql-directory-api tests

Add leo build, which is intended to be the "one-off for production" command. leo develop will turn into a webpack-dev-server style situation. Should think about whether leo develop or leo build --develop makes more sense.

TODO:

Docs

• Plugins
  • Pipeline/bundle plugin options
  • Scaffolding (client, static, html)
  • Adding Content Types to config (index, schema)
  • Post Processing (process.js)
• Commands (build, develop, update-schema, API)
• Creating Content Types from markdown files, Contentful, git repos, etc (How data is processed and the "API" is created)
• data as source of truth (urls, etc)
• leo.config.js

Other

• Update blog starter
• Deal with iconv-loader warning in static bundle? It's annoying for regular usage to show this.