Fix bug where the '(D)elete' option wouldn't show in neovim

[glacambre]

Because the script uses executable('vim') to check various things, the option to delete the swap file wasn't available on systems where Neovim is installed but vim isn't. This commit fixes this bug.

[chrisbra]

wouldn't it be better to check for v:progpath?

[glacambre]

You're probably right. I thought there was a specific reason for checking especially for "vim" and not v:progpath. The last commit implements your suggestion.

[chrisbra]

The reason was, that variable didn't exists back when I wrote the script ;) Please squash.

[glacambre]

Done! :)

[chrisbra]

thanks!