Option to disable -i

[swsnr]

In a proper Zsh setup with .zshenv, -i is redundant. Hence, it'd be nice to have a way to remove -i from the shell command line used by this package.

Before opening a PR, I'd like to discuss the implementation first, since we can essentially choose between to different approaches:

• Only make -i customizables with a boolean flag.
• Make the entire command line customizable, using a list option, whose default is ("-i").

I'd favour the latter, but I'd like to get your OK before implementing it.

[purcell]

Great, yes, I'm generally +1 on this.

I'm not sure about making the whole list customizable, since the order is important: we need -c and the printf expression to be together. So perhaps we could hardcode the -c expr part, and make the other args a customizable list?

And I think I'd still like the -i to be included by default, just to make it work out-of-the-box for more people: I don't fancy dealing with lots of tickets if we suddenly turn off -i. :-)

[swsnr]

@purcell That was exactly my idea, see #14.