write source maps after autoprefixer has run
write source maps after autoprefixer has run

Addresses https://github.com/floridoo/gulp-sourcemaps/issues/60

5t111111/gulp-rails-pipeline,vigetlabs/gulp-rails-pipeline,5t111111/gulp-rails-pipeline,5t111111/gulp-rails-pipeline,vigetlabs/gulp-rails-pipeline,vigetlabs/gulp-rails-pipeline