fix _decode_data. bump 1.59a1

Author: mylokin

memcache.py

@@ -304,7 +304,7 @@ def _decode_value(self, data):
         if not data:
             return data
 
-        if not str(data).startswith(TAGS_PREFIX):
+        if isinstance(data, six.string_types) and (not data.startswith(TAGS_PREFIX)):
             return data
 
         try:

setup.py

@@ -4,7 +4,7 @@
 
 
 setup(name="python-memcached",
-      version="1.59a",
+      version="1.59a1",
       description="Pure python memcached client",
       long_description=open("README.md").read(),
       author="Evan Martin",