Set old Stripe API version so pagination isn't broken

lib/index.js

@@ -26,6 +26,7 @@ function Cohorter (key, options) {
   if (!(this instanceof Cohorter)) return new Cohorter(key, options);
   if (!key) throw new Error('Stripe cohort requires a Stripe key.');
   this.stripe = Stripe(key);
+  this.stripe.setApiVersion('2014-03-13');
   this.options = defaults(options, { count: 100, concurrency: 1 });
   var self = this;
   return function () { self.cohort.apply(self, arguments); };
@@ -114,4 +115,4 @@ Cohorter.prototype.query = function (start, end, offset, callback) {
     debug('loaded %d customers with offset %d', customers.length, offset);
     callback(null, res);
   });
-};
+};