Make Adyen.util module Python 3 compatible (#26)

* Make adding maps Python 3 compatible by chaining

* Set encoding before hashing

Author: woochica

Adyen/util.py

@@ -3,6 +3,7 @@
 
 import re
 from functools import wraps
+from itertools import chain
 from collections import OrderedDict
 import base64
 import hmac
@@ -25,7 +26,7 @@ def escapeVal(val):
     #for k,v in ordered_request.items():
     #    signing_string.append(':'.join(k,escapeVal(v)))
 
-    signing_string = ':'.join(map(escapeVal, map(str,ordered_request.keys()) + map(str,ordered_request.values())))
+    signing_string = ':'.join(map(escapeVal, chain(map(str,ordered_request.keys()), map(str,ordered_request.values()))))
 
     return signing_string
 
@@ -47,8 +48,7 @@ def escapeVal(val):
 
     ordered_request = OrderedDict(sorted(dict_object.items(), key=lambda t: t[0]))
 
-    signing_string = ':'.join(map(escapeVal, map(str,ordered_request.keys()) + map(str,ordered_request.values())))
+    signing_string = ':'.join(map(escapeVal, chain(map(str,ordered_request.keys()), map(str,ordered_request.values()))))
 
-
-    hm = hmac.new(hmac_key, signing_string, hashlib.sha256)
+    hm = hmac.new(hmac_key, signing_string.encode('utf-8'), hashlib.sha256)
     return base64.b64encode(hm.digest())