Initial version

Works for the pixelfoo apps.

Limitations:
- Resizing the window is buggy.
- The frame rate argument has no effect.
- The update and render event logic should be reworked.
- Supports only single file executables, not interpreters with args
  (e.g. running an app as "python3 app.py" is not supported)
- Supports only RGB, not RGBW (yet)

.gitignore

@@ -0,0 +1,3 @@
+/target
+*~
+tarpaulin-report.html