ignore utf-8 decoding errors

Author: jtylh

redisearch/_util.py

@@ -4,6 +4,6 @@ def to_string(s):
     if isinstance(s, six.string_types):
         return s
     elif isinstance(s, six.binary_type):
-        return s.decode('utf-8')
+        return s.decode('utf-8','ignore')
     else:
         return s  # Not a string we care about