Skip stand-alone npm installation by default
Skip stand-alone npm installation by default

Node.js has included npm for a while now and it makes little sense to
install it separately by default. Hence, --without-npm has been
changed to --with-npm along with the related logic.

Associated parameter 'sanity checks' that don't make sense anymore
have been dropped as well.

simudream/nodeenv,Milstein/nodeenv,twmt/nodeenv,simudream/nodeenv,asottile/nodeenv,asottile/nodeenv,jamesblunt/nodeenv,jamesblunt/nodeenv,twmt/nodeenv,Milstein/nodeenv,chriskuehl/nodeenv,chriskuehl/nodeenv,jhermann/nodeenv