Initial python3 changes

Mostly just updating libraries, removing string encoding/decoding,
fixing some edge cases. No new functionality was added in this
commit.

lib/cherrypy/_json.py

@@ -0,0 +1,25 @@
+"""
+JSON support.
+
+Expose preferred json module as json and provide encode/decode
+convenience functions.
+"""
+
+try:
+    # Prefer simplejson
+    import simplejson as json
+except ImportError:
+    import json
+
+
+__all__ = ['json', 'encode', 'decode']
+
+
+decode = json.JSONDecoder().decode
+_encode = json.JSONEncoder().iterencode
+
+
+def encode(value):
+    """Encode to bytes."""
+    for chunk in _encode(value):
+        yield chunk.encode('utf-8')