Fixed rest of the ESLint issues and made it required on Travis-CI and in the webpack build

[ryanhugh]

• Fixed the rest of the ESLint issues
  • Disabled some of the a11y rules - we don't need to focus on making the site accessible now and can always come back to that
• Added eslint-loader to the webpack build so eslint will run when webpack is building the code and the build will fail if eslint fails
  • Not totally sure if we want to stick with this - maybe change a bunch of the errors to just warnings at this step?
  • But would still require that they pass on Travis
• Required that all the code passes linting on Travis

[edward-shen]

Seems good. Just gonna run it on my end to do one last check!