Non-optimal status code for redirect to https

[jrfnl]

Context: noticed this via a dead link/URL redirect checker.

When requesting http://getcomposer.org/ it redirects to https://getcomposer.org/ with status code 302 (= temporary redirect).

To verify, run curl -v http://getcomposer.org/

I believe it would be more optimal to redirect with a 301 (= permanent redirect) status code.

Not sure where to change this, so just opening this issue to draw attention to this.