Fix ESLint errors (#793)

This fixes failing `npm run lint`:

- fixes `max-len` issue in code by reformat of the expression
- exempt ES6 template literals from `max-len` rule using ESLint
  configuration change

Thanks!

.eslintrc

@@ -20,7 +20,7 @@
     "no-console": 0,
     "no-alert": 0,
     "no-underscore-dangle": 0,
-    "max-len": [1, 120, 2, {ignoreComments: true}],
+    "max-len": [1, 120, 2, {"ignoreComments": true, "ignoreTemplateLiterals": true}],
     "quote-props": [1, "consistent-as-needed"],
     "no-unused-vars": [1, {"vars": "local", "args": "none"}],
     "consistent-return": ["error", { "treatUndefinedAsUnspecified": true }],

client/modules/IDE/components/PreviewFrame.jsx

@@ -81,7 +81,10 @@ class PreviewFrame extends React.Component {
 
   handleConsoleEvent(messageEvent) {
     if (Array.isArray(messageEvent.data)) {
-      const decodedMessages = messageEvent.data.map(message => Object.assign(Decode(message.log), { source: message.source }));
+      const decodedMessages = messageEvent.data.map(message =>
+        Object.assign(Decode(message.log), {
+          source: message.source
+        }));
 
       decodedMessages.every((message, index, arr) => {
         const { data: args } = message;