goinstall: abort and warn when using any url scheme, not just 'http://'
goinstall: abort and warn when using any url scheme, not just 'http://'

R=golang-dev, rsc
CC=golang-dev
http://codereview.appspot.com/4801053

mhennings/marcohennings-go,scirelli/scirelli-go,d0f/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,npe9/noahevans-go9,d0f/go-zh,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,rdp/rogerpack2005-golang,mhennings/marcohennings-go,rdp/rogerpack2005-golang,webfd/go-zh,rdp/rogerpack2005-golang,Triskite/willstone-goclone,mhennings/marcohennings-go,sanjosh/sanjos100-tipc,npe9/noahevans-go9,webfd/go-zh,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,rdp/rogerpack2005-golang,webfd/go-zh,scirelli/scirelli-go,Triskite/willstone-goclone,webfd/go-zh,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,Triskite/willstone-goclone,rdp/rogerpack2005-golang,bryanxu/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,glycerine/jeaten-go-arrayof-structof,bryanxu/go-zh,mhennings/marcohennings-go,scirelli/scirelli-go,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,npe9/noahevans-go9,d0f/go-zh,Triskite/willstone-goclone,npe9/noahevans-go9,rdp/rogerpack2005-golang,Triskite/willstone-goclone,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,rflanagan/reginaldflanagan-project1,glycerine/jeaten-go-arrayof-structof,rdp/rogerpack2005-golang,npe9/noahevans-go9,d0f/go-zh,bryanxu/go-zh,rflanagan/reginaldflanagan-project1,npe9/noahevans-go9,rdp/rogerpack2005-golang,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,bryanxu/go-zh,Triskite/willstone-goclone,rflanagan/reginaldflanagan-project1,bryanxu/go-zh,bryanxu/go-zh,mhennings/marcohennings-go,d0f/go-zh,rflanagan/reginaldflanagan-project1,mhennings/marcohennings-go,npe9/noahevans-go9,mhennings/marcohennings-go,webfd/go-zh,Triskite/willstone-goclone,npe9/noahevans-go9,glycerine/jeaten-go-arrayof-structof,webfd/go-zh,sanjosh/sanjos100-tipc,mhennings/marcohennings-go,d0f/go-zh,glycerine/jeaten-go-arrayof-structof,scirelli/scirelli-go,glycerine/jeaten-go-arrayof-structof,rflanagan/reginaldflanagan-project1,webfd/go-zh