Guizero

- New [Drawing widget](drawing.md) for creating "drawings"
- Added full screen support for `App` and `Window`
- Doc updates
- Minor bug fixes
- contributors [martinohanlon](https://github.com/martinohanlon), [lawsie](https://github.com/lawsie)

- Refactoring of layout functions
- Enabled `align` for the `auto` layout
- `width` and `height` can now be set to `"fill"`
- Modified `setup.py` to restrict install to Python 3 only
- Minor bug fixes
- contributors [martinohanlon](https://github.com/martinohanlon), [bennuttal](https://github.com/bennuttall), [yeyeto2788](https://github.com/yeyeto2788), [knowledgejunkie](https://github.com/knowledgejunkie), [lawsie](https://github.com/lawsie)

- Fixed `Box` to size properly
- Added `border` to `Box`
- Added `width` and `height` to widget constructor
- Added `resize` method to all widgets
- Minor bug fixes
- contributors [martinohanlon](https://github.com/martinohanlon)

- Various bug fixes
- wrapping multiline `TextBox` data
- `ButtonGroup`, `ComboBox` now allow 0 options at init
- Minimum pillow version is now 4.3.0
- `update` method added to `Add` and `Window`
- contributors [martinohanlon](https://github.com/martinohanlon), [scotty3785](https://github.com/scotty3785), [MrYsLab](https://github.com/MrYsLab), [bsimmo](https://github.com/bsimmo)

- Refactoring of `ButtonGroup`, including API breaking change - if no hidden values are specified, `ButtonGroup.value` now returns the text value not a generate string number [178](https://github.com/lawsie/guizero/issues/178)
- A widgets properties `bg`, `text_color`, `text_size`, `font`, `width`, `height` can be restored by to their default by setting them to `None` [181](https://github.com/lawsie/guizero/issues/181)
- Slider is now sized properly when orientated vertically [186](https://github.com/lawsie/guizero/issues/186)
- `Combo` and `ButtonGroup` now support `append`, `insert`, `remove`, `clear` and depreciated `add_option` [180](https://github.com/lawsie/guizero/issues/180)
- Refactoring of class hierarchy
- Various bug fixes
- contributors [martinohanlon](https://github.com/martinohanlon)

- `App`, `Window`, `Box` now support the following properties and will cascade them to widgets within them:
- `bg`
- `text_color`
- `text_size`
- `font`
- `enabled`
- Introduced `ListBox`
- Bug fixes relating to `bg` and `text_color` causing widgets to change colour when selected
- Minor bug fixes with `CheckBox`, `Waffle` and `Combo`
- Documentation fixes and updates
- contributors to this release [martinohanlon](https://github.com/martinohanlon), [lawsie](https://github.com/lawsie), [Harlekuin](https://github.com/Harlekuin)