GitLab

Fixes #5653

* use https everywhere

* use https links on the files that are left

Also, removed some broken links and updated redirections.

This solves a problem of using the variable name `$path' which then
smashes the environment variable `$PATH' and messes up the session.

See https://github.com/robbyrussell/oh-my-zsh/pull/5343#issuecomment-243043098

The $OSTYPE variable is set at ZSH compile time and can be safely used
to determine the OS of the system. e.g. darwin (os x)