Heroku-style config output
Switch to only shell-style output
Lower-case variable names
Return formatted output as the "pretty" subcommand
Simplify longest-key finding
Use app_dir rather than app_root

apps_root would be PLUSHU_ROOT/apps, pretty sure I use app_dir in other places
Add get/set/unset commands
Add app-env hook
Populate readme with usage for commands and subcommands