Guietta

Added
- password input field
- timer_start() and timer_stop()

Added
- iterator protocol to loop through GUI events
- thread management options

Changed
- Refactored matlotlib and pyqtgraph code into separate files

Added
- PGI() widget for pyqtgraph images.
- pyqtgraph widgets: added magic properties for plots and images.
- property proxies with the proxy() method
- "undo" context manager for properties
- connect() now has a default signal name

Changed
- Workaround for bugs in some version of the "inspect" module.

Changed
- Compatibility with old Matplotlib versions (<2.1)

Added
- support for group boxes
- hierarchical layouts ("child" Gui instances) using property assignments
- font() method and construction keyword argument
- matplotlib widgets: added magic properties, subplots, arbitrary
calls upon redrawing.

Changed
- callback in background processing is now optional
- documentation on readthedocs is finally properly versioned