add cli commands for user invite

lib/api/user.js

@@ -29,5 +29,13 @@ function invite(emails, callback){
 };
 
 module.exports = {
-    invite: invite
+    invite: invite,
+    getUsage: function(){
+        return [
+            "${command} user invite <address>..."
+        ];
+    },
+    handleCli: function(subcommand, args, callback){
+        invite(args._.slice(4), callback)
+    }
 };