Tests/Infra: Update babel, webpack, karma stuff.

[ryan-roemer]

• https://github.com/istanbuljs/babel-plugin-istanbul and remove isparta-loader
• Update karma
• See if we can / want to / need to remove inject-loader webpack thing for client tests.
• Anything else appropriate
• Consider using FormidableLabs/eslint-config-formidable (Align code standards with those in Victory (defaults/configurations/walmart/es6-react) #554)
• Modern webpack