Use simplejson if present instead of the stdlib json module.

The simplejson parser drop-in compatible with the builtin python JSON
parser, but much faster. In particular, this makes operations like
reindexing quicker.

elasticsearch/connection/base.py

@@ -1,5 +1,8 @@
 import logging
-import json
+try:
+    import simplejson as json
+except ImportError:
+    import json
 
 from ..exceptions import TransportError, HTTP_EXCEPTIONS
 

elasticsearch/connection/memcached.py

@@ -1,5 +1,8 @@
 import time
-import json
+try:
+    import simplejson as json
+except ImportError:
+    import json
 
 from ..exceptions import TransportError, ConnectionError, ImproperlyConfigured
 from ..compat import urlencode

elasticsearch/serializer.py

@@ -1,4 +1,7 @@
-import json
+try:
+    import simplejson as json
+except ImportError:
+    import json
 from datetime import date, datetime
 from decimal import Decimal