sanitize merchantware order id

CHANGELOG

@@ -1,5 +1,6 @@
 = ActiveMerchant CHANGELOG
 
+* Strip non alpha numeric chars out of MerchantWare order number [cody]
 * Parse complete response of Authorize.net CIM gateway [Patrick Joyce]
 * Update to PayPal Sandbox URL for testing Payflow Pro Express Checkout. See Express Checkout for Payflow Pro guide [cody]
 * Provide a C_STATE value of "Outside United States" for SageGateway when processing international customers [cody]

lib/active_merchant/billing/gateways/merchant_ware.rb

@@ -179,7 +179,7 @@ def expdate(credit_card)
       end
       
       def add_invoice(xml, options)
-        xml.tag! "strOrderNumber", options[:order_id].to_s.slice(0, 25)
+        xml.tag! "strOrderNumber", options[:order_id].to_s.gsub(/[^\w]/, '').slice(0, 25)
       end
       
       def add_amount(xml, money, tag = "strAmount")