add guide for running tests
add guide for running tests

kkkyyy03/scssphp,webdevid/scssphp,webdevid/scssphp,leafo/scssphp,dleffler/scssphp,g105b/scssphp,dleffler/scssphp,webdevid/scssphp,g105b/scssphp,guilhermeblanco/scssphp,g105b/scssphp,dleffler/scssphp,leafo/scssphp,leafo/scssphp,guilhermeblanco/scssphp