add a reminder to recovery message that the failed command may need to be re-run
fix bug with using an array info method twice on one line

this also involved carving out an exception for $self:
-	you can't use an env var named $self now
-	but you probably shouldn't have done that anyway
refactor `Files` spec for custom command into more general trailing args spec

this will allow us to implement a way to create trailing args for custom commands which aren't files
-	e.g. commits, users/authors, etc
also took this opportunity to revamp the custom command parsing errors
-	changed wording on some
-	now properly handling die's from classlets
-	implemented unit tests for errors
finally made it so you can have trailing args that _aren't_ files  \o/