Update README.md

Author: seth-reeser

README.md

@@ -1,6 +1,7 @@
 Vagrant Host Manager
 ====================
 
+[![Gem](https://img.shields.io/gem/v/vagrant-hostmanager.svg)](https://rubygems.org/gems/vagrant-hostmanager)
 [![Gem](https://img.shields.io/gem/dt/vagrant-hostmanager.svg)](https://rubygems.org/gems/vagrant-hostmanager)
 [![Gem](https://img.shields.io/gem/dtv/vagrant-hostmanager.svg)](https://rubygems.org/gems/vagrant-hostmanager)
 [![Twitter](https://img.shields.io/twitter/url/https/github.com/smdahlen/vagrant-hostmanager.svg?style=social)](https://twitter.com/intent/tweet?text=Check%20out%20this%20awesome%20Vagrant%20plugin%21&url=https%3A%2F%2Fgithub.com%2Fsmdahlen%2Fvagrant-hostmanager&hashtags=vagrant%hostmanager&original_referer=)