Add ESLint as the default linter

- Create `.eslintrc` and `.eslintignore`
- Add the above files to `.npmignore`
- Save `eslint` to devDependencies
- Create task `npm run lint` that lints `lib` and `test` directory

Documentation: http://eslint.org

.eslintignore

@@ -0,0 +1 @@
+*.json

.eslintrc

@@ -0,0 +1,34 @@
+{
+    "env": {
+        "node": true,
+        "browser": true,
+        "mocha": true,
+        "commonjs": true
+    },
+
+    "extends": "eslint:recommended",
+
+    "rules": {
+        "indent": [
+            "error",
+            4,
+            { SwitchCase: 1 }
+        ],
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "quotes": [
+            "error",
+            "single"
+        ],
+        "semi": [
+            "error",
+            "always"
+        ],
+        "strict": 2,
+        "no-unused-vars": 2,
+        "no-cond-assign": 2,
+        "camelcase": 1
+    }
+}

.npmignore

@@ -1 +1,2 @@
 test
+.eslint*

package.json

@@ -5,7 +5,8 @@
   "author": "Mark <mark@remarkablemark.org>",
   "main": "index.js",
   "scripts": {
-    "test": "mocha"
+    "test": "mocha",
+    "lint": "eslint index.js \"lib/**\" \"test/**\""
   },
   "repository": {
     "type": "git",
@@ -26,6 +27,7 @@
     "htmlparser2": "^3.9.1"
   },
   "devDependencies": {
+    "eslint": "^3.3.1",
     "jsdomify": "^2.1.0",
     "mocha": "^3.0.2",
     "react": "^15.3.0",