dashboard: Don't highlight first heading row.
dashboard: Don't highlight first heading row.

The two heading rows were previously a little hard to pick out,
because they were alternately shaded like the commit rows.

R=adg
CC=golang-dev
http://codereview.appspot.com/5500074

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