PaperWM update v0.4 -> v0.5 (#322)

Update PaperWM from the upstream source at
https://github.com/mogenson/PaperWM.spoon

Changes include:
- floating layer
- untile windows on exit
- fix move window to space and focus space
- warn about unsupported tabs
- change default hotkeys
- watch screens for changes
- switch to left or right space
- reverse cycle window widths
- customize window ratios