Updates to the modern code style

Created by: vtereshyn

There are few changes in the code style. I've attached two screenshots with my changes. You can see that I simplified 'if statement' at first screenshot and you can see that I changed a string to template string at the second.

packages/create-react-app/index.js

@@ -43,16 +43,14 @@ var semver = currentNodeVersion.split('.');
 var major = semver[0];
 
 if (major < 4) {
-  console.error(
-    chalk.red(
-      'You are running Node ' +
-        currentNodeVersion +
-        '.\n' +
-        'Create React App requires Node 4 or higher. \n' +
-        'Please update your version of Node.'
-    )
-  );
-  process.exit(1);
+    console.error(
+        chalk.red(
+            `You are running Node ${currentNodeVersion}.
+Create React App requires Node 4 or higher.
+Please update your version of Node.`
+        )
+    );
+    process.exit(1);
 }
 
 require('./createReactApp');

packages/react-dev-utils/eslintFormatter.js

@@ -12,10 +12,8 @@ const stripAnsi = require('strip-ansi');
 const table = require('text-table');
 
 function isError(message) {
-  if (message.fatal || message.severity === 2) {
-    return true;
-  }
-  return false;
+  return !!(message.fatal || message.severity === 2);
+
 }
 
 function formatter(results) {