Allow configurable "no execute" regexes

[IamCarbonMan]

I feel like a lot of us could be more comfortable using this if we could set a regex or some other way of preventing the program from previewing commands that might be destructive (rm, dd, shutdown, etc).

[Mateusz Czapliński]

Thanks for the idea! My current plan is to disable "auto-execution" by default, and spawn the subprocess only after user presses Enter. I'm considering leaving an option to have the current "always executing" mode enabled via a parameter.

I'm closing this as a duplicate, as the general problem is already being discussed in #8.