Bring back encoding statement

This is required for Python2-Pytest.

Author: ehrenfeu

tests/test_iotools.py

@@ -1,4 +1,5 @@
 """Tests for `imcflibs.iotools`."""
+# -*- coding: utf-8 -*-
 
 import pytest
 import zipfile

tests/test_pathtools.py

@@ -1,4 +1,5 @@
 """Tests for `imcflibs.pathtools`."""
+# -*- coding: utf-8 -*-
 
 import pytest
 from imcflibs.pathtools import parse_path

tests/test_strtools.py

@@ -1,4 +1,5 @@
 """Tests for `imcflibs.strtools`."""
+# -*- coding: utf-8 -*-
 
 import pytest
 import os