html: only try to run tidy by default - not w3c
html: only try to run tidy by default - not w3c

The w3c checker goes out to the internet to get its results so disable
it by default.

wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,nikmartin/dotfiles,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup