Correct python_requires string

Support all 2.6 and 2.7 version of Python

Author: franzlst

setup.py

@@ -50,7 +50,7 @@
     packages=['jsonconversion'],
     package_dir={'': 'src'},  # tell distutils packages are under src
 
-    python_requires='<=2.7',
+    python_requires='==2.6.*,==2.7.*',
     setup_requires=['pytest-runner'],
     install_requires=[],
     tests_require=['pytest', 'numpy'],