Added condition requirement to simplejson

simplejson is a part of python 2.6.

Change-Id: I3a1d776918c8707f21532fe3b043a039b72d6704
Signed-off-by: Chuck Short <chuck.short@canonical.com>

setup.py

@@ -1,4 +1,5 @@
 import os
+import sys
 
 import setuptools
 
@@ -11,6 +12,9 @@ requires = parse_requirements()
 dependency_links = parse_dependency_links()
 write_git_changelog()
 
+if sys.version_info < (2, 6):
+    requires.append('simplejson')
+
 
 def read(fname):
     return open(os.path.join(os.path.dirname(__file__), fname)).read()