This allows us to use whatever mirror we want. This is needed since
the current mirror got outdaded and the script was failing to
retrieve some modules.

We will use 'http://cpan.metacpan.org

' by default now.

Change-Id: I2c44a10de7a10e9784bb39943851b03ac7e00a14
Reviewed-by: Tony Sarajärvi <tony.sarajarvi@digia.com>
Reviewed-by: Simo Fält <simo.falt@digia.com>
Reviewed-by: Janne Anttila <janne.anttila@digia.com>