[dependency] - Add select eslint-plugin-jsx-a11y rules to lint config. (#175)

This project is a really good use case to apply some accessibility
rules to the lint config. For beginners getting started with React, we
can also teach/enforce basic accessibility rules in the web at author
time.

For now, I’ve just applied to the rules that are listed in
`eslint-config-airbnb` because these are most real-world tested, and we
can continue to add.

Happy to help if there are any questions/issues/concerns about the
plugin!

package.json

@@ -44,6 +44,7 @@
     "eslint": "3.1.1",
     "eslint-loader": "1.4.1",
     "eslint-plugin-import": "1.10.3",
+    "eslint-plugin-jsx-a11y": "2.0.1",
     "eslint-plugin-react": "5.2.2",
     "extract-text-webpack-plugin": "1.0.1",
     "file-loader": "0.9.0",