chore: Add lint-staged and husky (#314)

Add lint-staged with an auto-fix configuration for all JS files.
See https://github.com/okonet/lint-staged

package.json

@@ -20,7 +20,8 @@
     "docs:deploy": "yarn docs:build && gh-pages --dist _book --remote upstream",
     "docs:serve": "gitbook serve",
     "release": ".scripts/publish",
-    "test": "nyc --reporter lcov ava packages/*/test"
+    "test": "nyc --reporter lcov ava packages/*/test",
+    "precommit": "lint-staged"
   },
   "devDependencies": {
     "ava": "^0.19.1",
@@ -40,10 +41,18 @@
     "gitbook-plugin-npmsearchlist": "^1.0.0",
     "gitbook-plugin-prism": "^2.2.0",
     "graph-data-structure": "^0.8.0",
+    "husky": "^0.14.3",
+    "lint-staged": "^4.1.3",
     "nyc": "^11.0.2",
     "oao": "0.8.4",
     "prettier": "^1.4.4",
     "semver": "^5.3.0",
     "webpack": "^2.6.1"
+  },
+  "lint-staged": {
+    "*.js": [
+      "eslint --fix",
+      "git add"
+    ]
   }
 }