Merge pull request #31 from pre-commit/readme_test

Add test for readme

tests/readme_test.py

+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import io
+
+import yaml
+
+
+def test_readme_contains_all_hooks():
+    readme_contents = io.open('README.md').read()
+    hooks = yaml.load(io.open('hooks.yaml').read())
+    for hook in hooks:
+        assert '`{0}`'.format(hook['id']) in readme_contents