Bump Pyflakes to 1.1.0

``pyflakes.messages.ImportStarUsage`` only got introduced in v 1.1.0

Fixes #21

Author: adhikasp

setup.py

@@ -34,5 +34,5 @@ def version():
         py_modules=['autoflake'],
         entry_points={
             'console_scripts': ['autoflake = autoflake:main']},
-        install_requires=['pyflakes>=1.0'],
+        install_requires=['pyflakes>=1.1.0'],
         test_suite='test_autoflake')