core: fix for working with python 3.3

The unfixed parse_querystring() raises the following exception
in Python 3.3:

  TypeError: Type str doesn't support the buffer API

Also removed iteritems() as it is deprecated and no longer
supported in Python 3.x

httpretty/compat.py

@@ -59,9 +59,19 @@ class BaseClass(object):
 
 try:  # pragma: no cover
     from urllib.parse import urlsplit, urlunsplit, parse_qs, quote, quote_plus, unquote
+    unquote_utf8 = unquote
 except ImportError:  # pragma: no cover
     from urlparse import urlsplit, urlunsplit, parse_qs, unquote
     from urllib import quote, quote_plus
+    def unquote_utf8(qs):
+        if isinstance(qs, text_type):
+            qs = qs.encode('utf-8')
+        s = unquote(qs)
+        if isinstance(s, byte_type):
+            return s.decode("utf-8")
+        else:
+            return s
+
 
 try:  # pragma: no cover
     from http.server import BaseHTTPRequestHandler

httpretty/core.py

@@ -50,6 +50,7 @@ from .compat import (
     urlsplit,
     parse_qs,
     unquote,
+    unquote_utf8,
     ClassTypes,
     basestring
 )
@@ -182,12 +183,11 @@ class HTTPrettyRequest(BaseHTTPRequestHandler, BaseClass):
         )
 
     def parse_querystring(self, qs):
-        expanded = decode_utf8(unquote(utf8(qs)))
-
+        expanded = unquote_utf8(qs)
         parsed = parse_qs(expanded)
         result = {}
-        for k, v in parsed.iteritems():
-            result[k] = map(decode_utf8, v)
+        for k in parsed:
+            result[k] = map(decode_utf8, parsed[k])
 
         return result