add badge

README.md

@@ -1,4 +1,5 @@
 # IU LDAP Groups Lookup
+[![Gem Version](https://badge.fury.io/rb/ldap_groups_lookup.svg)](https://badge.fury.io/rb/ldap_groups_lookup)
 
 ## Usage
 
@@ -73,4 +74,4 @@ Alternatively, create a file `config/ldap_groups_lookup.yml` that looks like:
 :member_whitelist:
   - OU=Groups
 ```
-Note: The yaml style does not allow for easy configuration of some properties like tls_options or other auth methods.
+Note: The yaml style does not allow for easy configuration of some properties like tls_options or other auth methods.