Drop support for EOL Python versions (#265)

* Drop support for EOL Python versions

* sudo no longer needed https://blog.travis-ci.com/2018-11-19-required-linux-infrastructure-migration

* Remove unittest2 dependency

* Add python_requires and Trove classifiers

* Replace unittest2 with unittest
diff --git a/setup.py b/setup.py
index fbf81b1..efd1117 100644
--- a/setup.py
+++ b/setup.py
@@ -39,7 +39,6 @@
 ]
 
 TESTING_PACKAGES = [
-    'unittest2>=0.5.1',
     'mock>=1.0.1',
 ]
 
@@ -62,6 +61,7 @@
     url='http://github.com/google/apitools',
     author='Craig Citro',
     author_email='craigcitro@google.com',
+    python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*',
     # Contained modules and scripts.
     packages=setuptools.find_packages(include=['apitools']),
     entry_points={'console_scripts': CONSOLE_SCRIPTS},
@@ -88,6 +88,10 @@
     # PyPI package information.
     classifiers=[
         'License :: OSI Approved :: Apache Software License',
+        'Programming Language :: Python :: 2',
+        'Programming Language :: Python :: 2.7',
+        'Programming Language :: Python :: 3',
+        'Programming Language :: Python :: 3.5',
         'Topic :: Software Development :: Libraries',
         'Topic :: Software Development :: Libraries :: Python Modules',
         ],