Added API method to gather the plugin version

src/main/java/fr/xephi/authme/api/NewAPI.java

@@ -69,6 +69,16 @@ public class NewAPI {
         return plugin;
     }
 
+    /**
+     * Gather the version number of the plugin.
+     * This can be used to determine whether certain API features are available or not.
+     *
+     * @return Plugin version identifier as a string.
+     */
+    public String getPluginVersion() {
+        return AuthMe.getPluginVersion();
+    }
+
     /**
      * Return whether the given player is authenticated.
      *