Add scss-lint checker for SCSS files
Add scss-lint checker for SCSS files

Add checker for linting and syntax checking SCSS files with `scss-lint`
(https://github.com/causes/scss-lint/).

wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup,wezhang/vim-setup