Add Python 3 trove classifier.

vaibhavsagar · vaibhavsagar · commit 3f68a5f43639 · 2015-11-09T18:40:35.000+11:00
This is so that tools like https://github.com/brettcannon/caniusepython3 work properly.
diff --git a/setup.py b/setup.py
@@ -21,5 +21,6 @@
           'Intended Audience :: Developers',
           'License :: OSI Approved :: MIT License',
           'Programming Language :: Python',
+          'Programming Language :: Python :: 3',
       ],
       )

Original file line number	Diff line number	Diff line change
`@@ -21,5 +21,6 @@`
`21`	`21`	`'Intended Audience :: Developers',`
`22`	`22`	`'License :: OSI Approved :: MIT License',`
`23`	`23`	`'Programming Language :: Python',`
	`24`	`+ 'Programming Language :: Python :: 3',`
`24`	`25`	`],`
`25`	`26`	`)`