Removes unicode header string from test files

tests/test_functions.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 from tableprint import top, bottom, row
 import pytest

tests/test_io.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 from tableprint import table, banner, dataframe
 from io import StringIO

tests/test_utils.py

@@ -1,4 +1,3 @@
-# -*- coding: utf-8 -*-
 from __future__ import unicode_literals
 from tableprint import humantime, _format_line, LineStyle
 import pytest