Pygame-menu

- Fixes 251, 252.
- Added v3 note.
- Improves docs.
- Added ``BaseImage`` methods ``get_path``, ``get_drawing_mode``, ``set_drawing_mode``, ``get_drawing_offset``, and ``set_drawing_offset``.
- New ``PYGAME_WINDOWCLOSE`` event locals.
- Fix several typing issues.
- Removed ``**kwargs`` from ``Menu`` constructor.
- Improve computation of max/min widget position.
- Improved widget positioning on Menu centering.
- New ``Menu`` method ``get_height`` and ``set_title``.
- New ``MenuBar`` widget method ``get_title_offset``.
- Fixed ``ScrollBar`` constructor parameter ``onchange``.
- New ``Widget`` methods ``get_position``, ``get_width``, ``get_height`` and ``get_size``.
- Fixed ``Selection`` ``get_height`` method.

- Fixed double widget background drawing, 246.
- New function ``is_event`` in ``pygame_menu.event`` module.
- New menu method ``set_onclose(onclose)`` and ``get_theme``.
- Added attributes to Menu.
- Now menu constructor copies the default theme.
- Set theme ``widget_background_inflate`` back to ``(0,0)``.
- Added widget ``selection_expand_background`` property and ``expand_background_inflate_to_selection_effect()`` method.
- Added ``set_backbox_border_width`` to ``MenuBar`` widget.
- Improve docs and tests.

- Docs fixes.
- Renamed ``BaseImage.apply_image_function`` ``func`` method to ``image_function``.
- Renamed widget method ``add_draw_callback`` ``func`` to ``draw_callback``.
- Renamed widget method ``add_update_callback`` ``func`` to ``update_callback``.

- Added widget transform methods ``rotate``, ``translate``, ``flip``, ``scale`` and ``rotate``.
- Fix ``BaseImage`` flip bug.
- Throw warning if Menu ``column_fit_text`` constructor parameter is enabled but ``column_max_width`` is None.
- Improve edge case while creating scrollarea if menubar height is greater than menu height.
- New menu methods ``get_menubar_widget()`` and ``get_scrollarea()``.
- New widget method ``get_surface``.

- Fixes widget padding if a background color is used, 242.
- New Menu parameter ``overflow``.
- Fix ``background_inflate`` docs.
- New Menu widget insertion parameter ``font_background_color``.
- New TextInput parameter ``input_underline_len``.
- New Menu method ``get_clock()``.
- New Theme ``widget_font_background_color`` property.
- New Selection method ``get_xy_margin()``.
- New Widget property ``lock_position``.
- New Widget methods ``has_attribute(key)``, ``remove_attribute(key)``, ``add_draw_callback(func)``, ``remove_draw_callback(callid)``, ``apply_draw_callbacks()``, ``add_update_callback(func)``, ``remove_update_callback(callid)``, ``apply_update_callbacks()``.
- Improve widget rendering.

This version introduces a lot of changes from v3.3.2:

Error fixes:
- Fixed widget resizing, 232.
- Fixed column calculation, 233.
- Fixed menu centering if the vertical widget offset is not zero, 230.
- Fixed submenu recursion while adding buttons to Menu, 241.
- Fixed callable assertion.
- Fix scroll area surface size computation with different thickness scrollbars.
- Fixed edge cases in Menu ``get_selected_widget()`` method.
- Fixed draw exceptions in ``LeftArrowSelection`` and ``RightArrowSelection``.
- Fixed exception while retrieving height of widget selection If it is None.
- Fixed submenu race if Menu is removed from button while using ``update_callback`` Button widget method.
- Fixed ``MenuBar`` widget back box status on certain conditions.
- Fixed widget selection in different edge cases (visibility, removal, unselectable).
- Fixed widget ``_font_render_string`` method if the font was not defined.

New methods:
- Added widget padding, 229.
- New widget methods ``hide()`` and ``show``, 237.
- ``Image`` widget now can be created directly from a ``BaseImage`` object.
- ``BaseImage`` new param ``load_from_file``.
- ``BaseImage`` new methods ``copy()``, ``apply_image_function(func)``, ``to_bw()`` and ``pick_channels(channels)``.
- ``BaseImage`` transforms methods now returns the object reference for nested calls.
- Added ``scrollarea_outer_margin`` to themes.
- Added ``back_count`` to ``add_button`` Menu method.
- Added ``margin_id`` parameter in ``add_vertical_margin`` Menu method. Now ``VMargin`` accepts ID.
- New Menu method ``add_generic_widget`` for adding generic widgets to the menu.
- Widget attributes now accepts ``margin`` as a list.
- New Menu method ``select_widget(widget)`` that sets widget as selected.
- New Menu method ``get_widgets()`` which returns the widgets as a tuple.
- New Menu method ``in_submenu(menu)`` for detecting submenus.
- New Widget method ``change_id(id)``.
- New Widget method ``update_font(style)`` for changing the style using previous styles.
- New ``Image`` widget methods ``get_image()`` and ``set_image(image)``.

Other changes:
- Added support for pygame v1.9.3.
- Added example with OOP style, 228.
- Improve widget access, 237.
- Improve documentation, module testing, and several typos.
- Added font cache for performance improvement.
- Improve menu centering in different circumstances.
- Widgets return ``True`` if render changed.

Changes that may break compatibility:
- Fixed ``Selector`` value in ``get_value()`` method. Now the entire tuple is returned instead of [0] item.
- Removed ``onchange`` unused parameter of ``Button`` widget.
- Removed ``onchange`` unused parameter of ``ScrollBar`` widget.
- Menu ``_check_id_duplicated`` method now returns ``IndexError`` instead of ``ValueError``.
- Menu ``get_selected_widget()`` method not returns ``None`` is no widget is selected instead of a ``ValueError`` exception.
- ``THEME_GREEN`` scrollbar thickness was established to 20px (previous were 14px).
- Adding recursive Menus now throws a ``ValueError`` exception.
- Widget ``get_selection_effect`` now returns a ``_NullSelection`` object instead of ``None`` if it is not stablished.