Super Simple GUI Library

[Ivan Trombley]

I started a new GUI library project (for various reasons) base on 
SDL2. It's pretty basic at the moment but I created a github 
repository so that I can hopefully get some feedback on it. What 
is currently present:

- App: an application struct housing the main loop.
- Handle: a RAII struct for conveneint handling of SDL pointers.
- Area: an abstract rectangular base class for UI items.
- BlankArea: a non-visible area that can have children.
- RenderArea: an area with children and a render delegate for 
custom drawing.
- VisibleArea: a basic visible area.
- TextArea: an area for displaying a single line of text.

The github repository is here:
https://github.com/Barugon/ssgl

Please let me know what you think.