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

@@ -1,4 +1,7 @@
 import logging
+try:
+    import simplejson as json
+except ImportError:
     import json
 
 from ..exceptions import TransportError, HTTP_EXCEPTIONS

elasticsearch/connection/memcached.py

@@ -1,4 +1,7 @@
 import time
+try:
+    import simplejson as json
+except ImportError:
     import json
 
 from ..exceptions import TransportError, ConnectionError, ImproperlyConfigured

elasticsearch/serializer.py

@@ -1,3 +1,6 @@
+try:
+    import simplejson as json
+except ImportError:
     import json
 from datetime import date, datetime
 from decimal import Decimal