Added extra 'modman-root-dir' that installs packages there instead of to the vendor-dir
Added check if source path exists
Added extra 'skip-package-deployment' that allows skipping deploying with any strategy. Having a modman-root-dir (see previous commit) is not supported by the current strategies because the wrong relative paths will be linked. You might want to fallback to the normal modman script here until the php version is stable and fully supports all classic modman features.