Guizero

- v0.5.0 includes significant refactoring of the guizero code base and introduces many new features
- New image functionality introduced when PIL is installed:
- images can be passed as `Tk.PhotoImage` or `PIL.Image` objects as well as file paths
- more images types are supported
- animated images (gifs) are supported
- images are scaled when the size is changed
- `ButtonGroup` - `selected` is now optional, `enabled` properties now supported, `value_text` fixed
- Fixed multiple `App` bug
- Created `Window` class to support multi-window applications
- Added `multiline` and `scrollbar` functionality to `TextBox`
- Refactored guizero to introduce a class hierarchy making guizero wide code changes easier to implement
- Added the following events to all widgets, this should be considered experimental in this release:
- `when_clicked`
- `when_left_button_pressed`
- `when_left_button_released`
- `when_right_button_pressed`
- `when_right_button_released`
- `when_key_pressed`
- `when_key_released`
- `when_mouse_enters`
- `when_mouse_leaves`
- `when_mouse_dragged`
- Various minor bug fixes
- Automated tests have been introduced
- contributors to this release [martinohanlon](https://github.com/martinohanlon), [scotty3785](https://github.com/scotty3785), [IDF31](https://github.com/IDF31), [drussell1974](https://github.com/drussell1974) - ta very much :)

- colors can now be specified as either `"red"`, `"ffffff"`, or `(red, green, blue)`
- change `Picture` `image` startup parameter to be optional
- updated `Picture` and `PushButton` errors and docs to show that PNG and GIF images can be used in Windows & Linux
- refactored `Waffle` resolving bugs that setting properties didnt change its appearance
- changed waffle so you can reference a pixel using `waffle[x,y]`
- added `text_color`, `text_size` and `font` properties to `Slider`
- added `width` and `height` properties to:
- `Box`
- `ButtonGroup`
- `CheckBox`
- `Combo`
- `Picture`
- `Slider`
- `Text`
- added `width` property to:
- `TextBox`
- contributors to this release [Coal0](https://github.com/coal0), [martinohanlon](https://github.com/martinohanlon), [scotty3785](https://github.com/scotty3785) - :)

- made `PushButton` `command` optional
- `Combo` command functions can now have 0 arguments
- `Waffle` command functions can now have 0 arguments
- refactored command functions and added `update_command` to:
- `ButtonGroup`
- `CheckBox`
- `Combo`
- `PushButton`
- `Slider`
- `Waffle`
- refactored `text_color`, `text_size` and `font` properties and added them to:
- `ButtonGroup`
- `Combo`
- `CheckBox`
- `PushButton`
- `Text`
- `TextBox`
- refactored `bg` (background) and added to:
- `Box`
- `ButtonGroup`
- `CheckBox`
- `Combo`
- `Picture`
- `PushButton`
- `Slider`
- `Text`
- `TextBox`
- contributors to this release [m4ddav3](https://github.com/m4ddav3), [Coal0](https://github.com/coal0), [lawsie](https://github.com/lawsie), [martinohanlon](https://github.com/martinohanlon) - :)

Minor features, bug fixes and internal refactoring

- added `xspan`, `yspan` to grid layout (Credit: [penguintutor](https://github.com/penguintutor))
- fixed `show()` for widgets in a grid layout
- added `master`, `grid`, `align` and `visible` properties to widgets
- added `layout` property to containers
- fixed `Waffle` `height` (Credit: [scotty3785](https://github.com/scotty3785))
- minor doc updates

Bug fixes and deployment test

- PushButton bug fixes
- added `enabled` property to widgets which support `Enable` / `Disable`
- documentation tidy up
- added build notes to documentation