Use default SSL context when possible

https://docs.python.org/2/library/ssl.html#best-defaults

Deal with older Pythons which didn't do certificate validation, have
sane defaults or even provided a cipher string.

setup.py

@@ -7,6 +7,12 @@ setup(
     version="1.6.0",
     author="Amr Hassan <amr.hassan@gmail.com>",
     install_requires=['six'],
+    # FIXME This can be removed after 2017-09 when 3.3 is no longer supported
+    # and pypy3 uses 3.4 or later, see
+    # https://en.wikipedia.org/wiki/CPython#Version_history
+    extras_require={
+        ':python_version=="3.3"': ["certifi"],
+    },
     tests_require=['mock', 'pytest', 'coverage', 'pep8', 'pyyaml', 'pyflakes'],
     description=("A Python interface to Last.fm and Libre.fm"),
     author_email="amr.hassan@gmail.com",