feat(gen): add note about being prerelease version

Author: Awk34

Diff for: app/generator.js

@@ -37,6 +37,12 @@ export default class Generator extends Base {
       },
 
       info: function () {
+        this.log(chalk.red(`
+################################################################
+# NOTE: You are using a pre-release version of
+# generator-angular-fullstack. For a more stable version, run
+# \`npm install -g generator-angular-fullstack@^2.0.0\`
+################################################################`));
         this.log(this.yoWelcome);
         this.log('Out of the box I create an AngularJS app with an Express server.\n');
       },