Do not run if node version older than 5.9

cli.js

@@ -21,6 +21,7 @@
 const meow = require('meow');
 const lighthouse = require('./');
 const log = require('npmlog');
+const semver = require('semver');
 const Printer = require('./cli/printer');
 const cli = meow(`
   Usage
@@ -38,6 +39,11 @@ const cli = meow(`
 const defaultUrl = 'https://m.flipkart.com';
 const url = cli.input[0] || defaultUrl;
 
+if (semver.lt(process.version, '5.9.0')) {
+  console.error('Lighthouse requires node version 5.9 or newer');
+  process.exit(1);
+}
+
 lighthouse({
   url: url,
   flags: cli.flags

package.json

@@ -32,6 +32,7 @@
     "devtools-timeline-model": "1.0.16",
     "meow": "^3.7.0",
     "npmlog": "^2.0.3",
+    "semver": "^5.1.0",
     "traceviewer": "^1.0.8"
   },
   "devDependencies": {