Truly exclude 'tests' package in setup.py

This way setuptools certainly won't install it.

Author: maksbotan

setup.py

@@ -12,7 +12,7 @@
     url='https://github.com/django-debug-toolbar/django-debug-toolbar',
     download_url='https://pypi.python.org/pypi/django-debug-toolbar',
     license='BSD',
-    packages=find_packages(exclude=('tests', 'example')),
+    packages=find_packages(exclude=('tests.*', 'tests', 'example')),
     install_requires=[
         'django>=1.4.2',
         'sqlparse',