Use POSIX sed to upgrade version of spaceship (#430)
Use POSIX sed to upgrade version of spaceship (#430)

`sed -i` isn't POSIX compliant and behaves differently on BSD `sed` and GNU `sed`.

BSD `sed` with `-i` expects an extension after space. While this extension is optional on GNU `sed` and must be on the same argument without any intervening space. This breaks cross compatibility of script.
denysdovhan/spaceship-zsh-theme