tox: Update flake8-string-format to 0.2.2

- Do not check simple expressions, except for docstrings, because they
  cannot be accessed anyway.
- Properly assert starred arguments in Python 3.5. Only the last element
  must be a vararg if varargs are present and not the complete list.
- Output correct column offset on Python 3.4.2, as that used the wrong
  offset inside calls.

tox.ini

@@ -161,7 +161,7 @@ deps =
     flake8-mock==0.2
     flake8-pep3101==0.3
     flake8-putty==0.3.2
-    flake8-string-format==0.2.1
+    flake8-string-format==0.2.2
     flake8-tidy-imports==1.0.0
     flake8-tuple==0.2.9
     hacking==0.11.0