added cloning instructions to Contributing.md
added cloning instructions to Contributing.md

ReadyResponder/ReadyResponder,kgf/lims,houhoulis/ReadyResponder,pcai/lims,moritzsternemann/ReadyResponder,dusty-wil/ReadyResponder,ReadyResponder/ReadyResponder,dusty-wil/ReadyResponder,ReadyResponder/ReadyResponder,moritzsternemann/ReadyResponder,david135/lims,houhoulis/ReadyResponder,dusty-wil/ReadyResponder,houhoulis/ReadyResponder,moritzsternemann/ReadyResponder,moritzsternemann/ReadyResponder,david135/lims,houhoulis/ReadyResponder,ReadyResponder/ReadyResponder,david135/lims,kgf/lims,david135/lims,pcai/lims,pcai/lims,kgf/lims,pcai/lims,dusty-wil/ReadyResponder,kgf/lims