RFC: Confirmation on major stack actions

[pingram3030]

If run without --no-interactive the user is prompted for a literal yes prior to running an update, but there is zero confirmation for delete; this scares me.

Instead of having separate confirmation clauses for major actions I toyed with having a simple shared function, possibly in lib/command_line.rb, that can be used by delete, update, and possibly deploy, to ensure safety from humans being human. Would this be desired by others and is command_line the best place for this?