made Makefile self documenting
made Makefile self documenting

fixes #2169

ehartsuyker/securedrop,heartsucker/securedrop,garrettr/securedrop,garrettr/securedrop,conorsch/securedrop,micahflee/securedrop,heartsucker/securedrop,heartsucker/securedrop,micahflee/securedrop,conorsch/securedrop,conorsch/securedrop,garrettr/securedrop,micahflee/securedrop,ehartsuyker/securedrop,conorsch/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,ehartsuyker/securedrop,micahflee/securedrop,garrettr/securedrop