Add simplejson 2.1.0 and use it when it's not already installed.

third_party/simplejson/PKG-INFO

+Metadata-Version: 1.0
+Name: simplejson
+Version: 2.1.0
+Summary: Simple, fast, extensible JSON encoder/decoder for Python
+Home-page: http://undefined.org/python/#simplejson
+Author: Bob Ippolito
+Author-email: bob@redivi.com
+License: MIT License
+Description: 
+        simplejson is a simple, fast, complete, correct and extensible
+        JSON <http://json.org> encoder and decoder for Python 2.4+.  It is
+        pure Python code with no dependencies, but includes an optional C
+        extension for a serious speed boost.
+        
+        simplejson was formerly known as simple_json, but changed its name to
+        comply with PEP 8 module naming guidelines.
+        
+        The encoder may be subclassed to provide serialization in any kind of
+        situation, without any special support by the objects to be serialized
+        (somewhat like pickle).
+        
+        The decoder can handle incoming JSON strings of any specified encoding
+        (UTF-8 by default).
+        
+Platform: any
+Classifier: Intended Audience :: Developers
+Classifier: License :: OSI Approved :: MIT License
+Classifier: Programming Language :: Python
+Classifier: Topic :: Software Development :: Libraries :: Python Modules