More mypy (#612)

* remove type comment where type is annotated
* move function tests
* remove six from tests
* add none annotations
* add more types
* change mock (so that mypy understands it)

test/test_functions/test_function_cut.py

@@ -0,0 +1,10 @@
+import escpos.printer as printer
+from escpos.constants import GS
+
+
+def test_cut_without_feed() -> None:
+    """Test cut without feeding paper"""
+    instance = printer.Dummy()
+    instance.cut(feed=False)
+    expected = GS + b"V" + bytes((66,)) + b"\x00"
+    assert instance.output == expected