linter: Fix UnicodeError when parsing comments

And add tests when reading non-ASCII strings and comments (both from
Python strings and from files).

Fixes: #10

tests/test_linter.py

@@ -44,3 +44,15 @@ class LinterTestCase(unittest.TestCase):
     def test_run_on_list(self):
         self.assertRaises(TypeError, linter.run,
                           ['h', 'e', 'l', 'l', 'o'], self.fake_config())
+
+    def test_run_on_non_ascii_chars(self):
+        s = (u'- hétérogénéité\n'
+             u'# 19.99 €\n')
+        linter.run(s, self.fake_config())
+        linter.run(s.encode('utf-8'), self.fake_config())
+        linter.run(s.encode('iso-8859-15'), self.fake_config())
+
+        s = (u'- お早う御座います。\n'
+             u'# الأَبْجَدِيَّة العَرَبِيَّة\n')
+        linter.run(s, self.fake_config())
+        linter.run(s.encode('utf-8'), self.fake_config())