Adds remove-tabs hook

Inpired by initial work done by Lucas-C:
https://github.com/Lucas-C/pre-commit-hooks

tests/remove_tabs_test.py

@@ -0,0 +1,31 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import pytest
+
+from pre_commit_hooks.remove_tabs import main as remove_tabs
+
+
+@pytest.mark.parametrize(
+    ('input_s', 'expected'),
+    (
+        ('foo \t\nbar', 'foo     \nbar'),
+        ('bar\n\tbaz\n', 'bar\n    baz\n'),
+    ),
+)
+def test_remove_tabs(input_s, expected, tmpdir):
+    path = tmpdir.join('file.txt')
+    path.write(input_s)
+    assert remove_tabs(('--whitespaces-count=4', path.strpath)) == 1
+    assert path.read() == expected
+
+
+@pytest.mark.parametrize(('arg'), ('', '--', 'a.b', 'a/b'))
+def test_badopt(arg):
+    with pytest.raises(SystemExit) as excinfo:
+        remove_tabs(['--whitespaces-count', arg])
+    assert excinfo.value.code == 2
+
+
+def test_nothing_to_fix():
+    assert remove_tabs(['--whitespaces-count=4', __file__]) == 0