Fix eslint errors

.eslintrc.js

@@ -0,0 +1,42 @@
+module.exports = {
+    "env": {
+        "browser": true,
+        "commonjs": true,
+        "es6": true,
+        "node": true
+    },
+    "globals": {
+        "ePub": true,
+        "JSZip": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+        "sourceType": "module"
+    },
+    "rules": {
+        "indent": [
+            "error",
+            "tab",
+            { "VariableDeclarator": { "var": 2, "let": 2, "const": 3 } }
+        ],
+        "linebreak-style": [
+            "error",
+            "unix"
+        ],
+        "quotes": [
+            "warn",
+            "double"
+        ],
+        "semi": [
+            "error",
+            "always"
+        ],
+        "no-unused-vars" : ["warn"],
+        "no-console" : ["warn"],
+        "no-unused-vars": [
+          "error",
+          { "vars": "all", "args": "none" }
+        ],
+        "no-mixed-spaces-and-tabs": ["error", "smart-tabs"]
+    }
+};