Check for Node v6 or later (#80)

package.json

@@ -57,6 +57,7 @@
     "commander": "^2.9.0",
     "generator-feathers": "1.0.2",
     "generator-feathers-plugin": "0.10.0",
+    "semver": "^5.3.0",
     "yeoman-environment": "^1.6.6"
   },
   "devDependencies": {

src/index.js

@@ -1,6 +1,7 @@
 import yeoman from 'yeoman-environment';
 import program from 'commander';
 import meta from 'generator-feathers/meta';
+import semver from 'semver';
 
 const env = yeoman.createEnv();
 
@@ -23,6 +24,11 @@ module.exports = function(argv, generatorOptions = {
   program.version(require('../package.json').version)
     .usage('generate [type]');
 
+  if(!semver.satisfies(process.version, '>= 6.0.0')) {
+    console.error('The Feathers CLI and generated application requires Node v6.0.0 or later.');
+    return process.exit(1);
+  }
+
   program.command('generate [type]')
     .alias('g')
     .description(description)