Add a requirements.txt.

Also use it within setup.py. It doesn't seem possible to define dependencies for tox with install_requires.

test/test_parso_integration/test_parser_utils.py

@@ -1,4 +1,6 @@
-from jedi._compatibility import u, is_py3
+# -*- coding: utf-8 -*-
+
+from jedi._compatibility import is_py3
 from jedi import parser_utils
 from parso.python import parse
 from parso.python import tree
@@ -67,7 +69,7 @@ def test_hex_values_in_docstring():
     if is_py3:
         assert doc == '\xff'
     else:
-        assert doc == u('<EFBFBD>')
+        assert doc == u'<EFBFBD>'
 
 
 @pytest.mark.parametrize(