Update wdns.pyx

Fix for the following stack trace;
  File "wdns.pyx", line 593, in wdns.parse_message
  File "wdns.pyx", line 858, in wdns.edns.__init__
TypeError: Expected str, got bytes
farsightsec#19

wdns.pyx

@@ -845,10 +845,10 @@ cdef class edns(object):
     @ivar size: Maximum message size
     @type size: int
     """
-    cdef public str options
+    cdef public bytes options
     """
     @ivar options: OPT RR contents
-    @type options: str
+    @type options: bytes
     """
 
     def __init__(self, version, flags, size, options):