Add python_requires to setup.py

Author: mwilliamson

Diff for: setup.py

@@ -20,6 +20,7 @@ def read(fname):
     packages=['precisely'],
     keywords="matcher matchers",
     install_requires=[],
+    python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*',
     classifiers=[
         'Development Status :: 5 - Production/Stable',
         'Intended Audience :: Developers',
@@ -34,4 +35,3 @@ def read(fname):
         'Programming Language :: Python :: 3.7',
     ],
 )
-