Shopify/active_merchant — pull request #640 by melari (2013-04-01 13:53:31+00:00)
Title: PxPay: Trim MerchantReferences longer than 50 characters.

**Problem**
This is actually the same issue as #583, just for their offsite gateway PxPay.

**Changes**
Trim down any MerchantReference longer than 50 characters.

**Review**
@jduff
cc @silverstreaked