[wip][rfc] shell version(posix compatible)

[lucasts]

This a working in progress implementation.

goals:

• remain posix compatible(aka: work with most shells(zsh and bash top priority)
• mimic all current lunchy features
• integrate with homebrew(easy install)

that said, I'm opening this PR as a request for comments.

I will work in the Easter holiday in it and I expect to have a almost 100% compatible version next weekend.

@mperham: what do you think?

anyway, Thanks a lot for lunchy, it's a time saver!

[lucasts]

I'm on linux this weekend, that's the reason I echoed most final commands 🐹

sorry about that, If any good fellow want to test it, just remove echo and outer "

[lucasts]

most commands are done

There some refactors lefts to do(most extract code duplication) and apply some options.

[huyz]

What is the purpose of this PR? A complete reimplementation?