add get-latest-statement method.

lib/charged.js

@@ -206,6 +206,26 @@ Charged.prototype.getSubscriptionStatements = function(name, options, callback)
   return this.get(path, options, callback, 'statement');
 };
 
+Charged.prototype.getLatestStatement =
+Charged.prototype.getLatestSubscriptionStatement = function(sub, callback) {
+  var self = this;
+
+  var opt = {
+    per_page: 100000
+    // order: 'oldest_first'
+  };
+
+  return this.getSubscriptionStatementIds(sub, opt, function(err, ids) {
+    if (err) return callback(err);
+
+    if (!ids.length) {
+      return callback(new Error('Not found.'));
+    }
+
+    return self.getStatement(ids.pop(), callback);
+  });
+};
+
 Charged.prototype.getStatement = function(name, callback) {
   var path = '/statements/' + escape(name);
   return this.get(path, callback, 'statement');