Typo

setup.py

@@ -4,7 +4,7 @@ setup(name='Mastodon.py',
       version='1.0.1',
       description='Python wrapper for the Mastodon API',
       packages=['mastodon'],
-      install_requires=['requests', 'dateutil'],
+      install_requires=['requests', 'dateutils'],
       url='https://github.com/halcy/Mastodon.py',
       author='Lorenz Diener',
       author_email='lorenzd+mastodonpypypi@gmail.com',