ref: Unify code style using Prettier and update ESLint rules

* Add Prettier, precommit hook using Husky and update ESLint to play nicely with Prettier.
* Run new code-style setup on all relevant .js files, without any changes in the code itself.
* Update ESLint version and unify package.json with the one from raven-node.
* Add lint script to package.json and configure .eslintignore, so it can be used by Grunt and npm.

Author: kamilogorek

.eslintignore

@@ -0,0 +1,6 @@
+build/
+dist/
+example/
+vendor/
+test/
+

.eslintrc

@@ -11,29 +11,16 @@
   },
   "rules": {
     "block-scoped-var": 2,
-    "comma-dangle": [2, "never"],
-    "dot-notation": [
-      2,
-      {
-        "allowKeywords": false
-      }
-    ],
-    "eqeqeq": [
-      2,
-      "allow-null"
-    ],
+    "dot-notation": [2, {"allowKeywords": false}],
+    "eqeqeq": [2, "allow-null"],
     "guard-for-in": 2,
     "new-cap": 2,
     "no-caller": 2,
-    "no-cond-assign": [
-      2,
-      "except-parens"
-    ],
+    "no-cond-assign": [2, "except-parens"],
     "no-debugger": 2,
     "no-empty": 2,
     "no-eval": 2,
     "no-extend-native": 2,
-    "no-extra-parens": 2,
     "no-irregular-whitespace": 2,
     "no-iterator": 2,
     "no-loop-func": 2,
@@ -44,29 +31,13 @@
     "no-sequences": 2,
     "no-shadow": 2,
     "no-undef": 2,
-    "no-unused-vars": [
-      2,
-      {"args": "none"}
-    ],
+    "no-unused-vars": [2, {"args": "none"}],
     "no-with": 2,
-    "quotes": [
-      2,
-      "single",
-      "avoid-escape"
-    ],
-    "semi": [
-      0,
-      "never"
-    ],
-    "strict": [
-      2,
-      "global"
-    ],
-    "valid-typeof": 2,
-    "wrap-iife": [
-      2,
-      "inside"
-    ],
-    "eol-last": 2
-  }
+    "semi": [0, "never"],
+    "strict": [2, "global"],
+    "valid-typeof": 2
+  },
+  "extends": [
+    "prettier"
+  ]
 }