Only show instead of open the repository or homepage URL

Small but useful option to show instead of launching the repository or homepage URL.

use:  with -s or --show option
$composer home monolog/monolog -Hs
Homepage URL: http://github.com/Seldaek/monolog

$composer home monolog/monolog --show  (or -s)
Repository URL: http://github.com/Seldaek/monolog