Refactor deprecated pkg_resources usage

- Locate resources relative to `__file__`
- Support egg/zip with `open_file_for_reading`

tests/test_input.py

@@ -0,0 +1,29 @@
+import propka.input as m
+import zipfile
+
+
+def test_open_file_for_reading(tmp_path):
+    path = tmp_path / "tmp.txt"
+    path.write_text("One\nTwo\nThree\n")
+    # str
+    with m.open_file_for_reading(str(path)) as outer:
+        assert outer.read() == "One\nTwo\nThree\n"
+    assert outer.closed
+    # Path
+    with m.open_file_for_reading(path) as outer:
+        # TextIO
+        with m.open_file_for_reading(outer) as inner:
+            assert inner.readline() == "One\n"
+        assert not outer.closed
+        assert outer.readline() == "Two\n"
+    assert outer.closed
+
+
+def test_open_file_for_reading__zipfile(tmp_path):
+    zippath = tmp_path / "tmp.zip"
+    arcname = "foo/bar.txt"
+    with zipfile.ZipFile(zippath, "w") as ziphandle:
+        ziphandle.writestr(arcname, "One\nTwo\nThree\n")
+    with m.open_file_for_reading(zippath / arcname) as outer:
+        assert outer.readline() == "One\n"
+    assert outer.closed