Fix me.save; remember added keys.
Merge branch 'master' into 1.0.0-dev
[#297] Make me.ObjectContainer.getEntityByProp return nested continers.
[297] Update CHANGELOG
[#300] Better me.event.KEYDOWN and KEYUP support

- Also adds better documentation, including examples.
Normalize documentation (no code changes)
[#310] cached the computed value of `hWidth` and `hHeight` values so that we avoid doing 2 divisions at each frame change
Merge branch 'master' into 1.0.0-dev
Merge branch `1.0.0-dev` into ticket-103-clean