node version check

bin/cli.js

@@ -1,2 +1,16 @@
 #!/usr/bin/env node
-require('../lib/cli-app').run()
+function validNodeVersion () {
+  var valid = false
+  try {
+    const semver = require('semver')
+    debugger
+    valid = semver.gte(require('process').version, '7.6.0')
+  } catch (err) {}
+  return valid
+}
+
+if (validNodeVersion()) {
+  require('../lib/cli-app').run()
+} else {
+  console.log('Sorry, this app requires node v7.6.0 or above. Please upgrade https://nodejs.org/en/')
+}