Add testing for newer Python versions 3.5 and 3.6

Include all supported Python versions as trove classifiers. Helps
library users know, at a glance, if the library can be integrated with
a project.

Remove Python 2.6 trove classifier, support was removed in
9bcf955af8

Also add trove classifier for PyPy as it is included in the tox test
matrix.

Change-Id: Iff7dcec47260006b325e3059cfaf8b8e912d2318

setup.cfg

@@ -15,9 +15,12 @@ classifier =
     Programming Language :: Python
     Programming Language :: Python :: 2
     Programming Language :: Python :: 2.7
-    Programming Language :: Python :: 2.6
     Programming Language :: Python :: 3
     Programming Language :: Python :: 3.4
+    Programming Language :: Python :: 3.5
+    Programming Language :: Python :: 3.6
+    Programming Language :: Python :: Implementation :: CPython
+    Programming Language :: Python :: Implementation :: PyPy
     Topic :: Software Development :: Testing
 test_suite = requests_mock.tests
 

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py34,py27,pypy,pep8
+envlist = py36,py35,py34,py27,pypy,pep8
 
 [testenv]
 setenv =