Webapp Sub-generator Improvements

✨NEW✨

• ✨ Removed csslint from webapp build chain and added stylelint as PostCSS plugin
• ✨ Added morphdom renderer shim to webapp generator (integrated by default)
• ✨ Added redux.state plugin to webapp generator (integrated by default)
• ✨ radio.logging plugin integrated by default
• ✨ Added Babel integration to webapp build chain
• ⚠️ Replaced PhantomJS with headless chrome (template files are now written using ES6 syntax)
• ⚠️ Removed marionette.radio.shim from webapp generator (since scaffolded web apps use Marionette v3)
• ⚠️ Renamed Handlebars shim --> mn.handlebars.templates.shim.js

🚧 Maintenance 🚧

• Added more ES6 syntax to tests
• Refactored tests to be less redundant and more maintainable
• Bumped dependencies
• Various syntax fixes and improvements
• Removed remaining Underscore.js code from webapp generator