Fix emitcss#59

Merged

Rich-Harris merged 4 commits intosveltejs:masterfrom

kaisermann:fix-emitcss

May 1, 2018

Commits on Apr 21, 2018

Generate components CSS on virtual files
kaisermann
committed

Commits on Apr 25, 2018

Commits on Apr 29, 2018

Only write virtual files if there's a webpack instance initialized. Make cssEmit test pass
kaisermann
committed