Merge remote-tracking branch 'upstream/master'

Author: Maksim Rafalko

src/Omnipay/PayPal/Message/RefundRequest.php

@@ -24,6 +24,11 @@ public function getData()
 
         $data['TRANSACTIONID'] = $this->getTransactionReference();
         $data['REFUNDTYPE'] = 'Full';
+        if ($this->getAmountDecimal() > 0) {
+            $data['REFUNDTYPE'] = 'Partial';
+            $data['AMT'] = $this->getAmountDecimal();
+            $data['CURRENCYCODE'] = $this->getCurrency();
+        }
 
         return $data;
     }