Exclude tests from distribution.

The tests package is found as a package due to presence of __init__.py. Use include to ensure only pygments gets installed.

setup.py

@@ -33,7 +33,7 @@
     description = 'Pygments is a syntax highlighting package written in Python.',
     long_description = __doc__,
     keywords = 'syntax highlighting',
-    packages = find_packages(),
+    packages = find_packages(include=['pygments']),
     entry_points = {
         'console_scripts': ['pygmentize = pygments.cmdline:main'],
     },