update to reflect new protocol when we are on new site.  Also to update download links

git-svn-id: http://svn.osgeo.org/postgis/trunk@10979 b70326c6-7e19-0410-871a-916f4a2858ee
fix formatting and word changes to tiger extension install section

git-svn-id: http://svn.osgeo.org/postgis/trunk@10981 b70326c6-7e19-0410-871a-916f4a2858ee