Fix array normalization (contentful#34)

Author: dlitvakb

CHANGELOG.md

@@ -1,6 +1,8 @@
 # CHANGELOG
 
 ## Unreleased
+### Fixed
+* Ensure all arrays sent as parameters to the API are properly serialized.
 
 ## v1.9.0
 ### Added

contentful/client.py

@@ -513,7 +513,7 @@ def _normalize_query(self, query):
 
         for k, v in query.items():
             if isinstance(v, list):
-                query[k] = ','.join(v)
+                query[k] = ','.join([str(e) for e in v])
 
     def _http_get(self, url, query):
         """