Add --destdir + document --destdir, --prefix and --libdir
Add --destdir + document --destdir, --prefix and --libdir

Should help #202

rdavison/jbuilder,rdavison/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,dra27/jbuilder,dra27/jbuilder,janestreet/jbuilder,janestreet/jbuilder,janestreet/jbuilder,dra27/jbuilder,janestreet/jbuilder,dra27/jbuilder