Do not print the source when provided with -q

When users specify any number of -q's on the command-line, we should not
show the source even if they have otherwwise configured Flake8 to do so.

Closes #245

tests/unit/test_nothing_formatter.py

@@ -0,0 +1,28 @@
+"""Tests for the Nothing formatter obbject."""
+import optparse
+
+from flake8 import style_guide
+from flake8.formatting import default
+
+
+def options(**kwargs):
+    """Create an optparse.Values instance."""
+    kwargs.setdefault('output_file', None)
+    kwargs.setdefault('tee', False)
+    return optparse.Values(kwargs)
+
+
+def test_format_returns_nothing():
+    """Verify Nothing.format returns None."""
+    formatter = default.Nothing(options())
+    error = style_guide.Error('code', 'file.py', 1, 1, 'text', '1')
+
+    assert formatter.format(error) is None
+
+
+def test_show_source_returns_nothing():
+    """Verify Nothing.show_source returns None."""
+    formatter = default.Nothing(options())
+    error = style_guide.Error('code', 'file.py', 1, 1, 'text', '1')
+
+    assert formatter.show_source(error) is None