Change interpreter to zsh

[jgreat]

Description

Change interpreter in install/uninstall scripts to zsh, for issue #338

Could do bash instead, but I figure if you're installing a zsh theme you probably have zsh installed.

[salmanulfarzy]

Good catch. For anyone looking for more info DashAsBinSh

[denysdovhan]

I've renamed un/installers to use sh, because some plugin managers (like zgen) have been sourcing these files. I'm afraid this PR may break the installation for some users.

[maximbaz]

Interesting, do you remember how sourcing can be a problem?

[denysdovhan]

@maximbaz when you source these files you just stuck in the installation process forever. Every time you open a terminal it executes installation script.

[maximbaz]

Not exactly sure how changing the interpreter fixes this, but maybe we can set bash instead of sh ? Someone reported that bash also works, contrary to sh.

[denysdovhan]

I meant file extension. zgen sources all files with zsh extension.

As for me, it's not okay, to have sh extension for file that is executed with zsh. It's like executing a file with py extension but using node interpreter.

[maximbaz]

I honestly don't see this as a big deal, it's a shell script one way or another, just a different interpreter that is used to execute it.