add scale-hsla function to work with latest mapnik-reference: https://github.com/mapnik/mapnik-reference/commit/66502bfde05a358844a96b1818c2059a01a31fa0
add support for direct-image-filters
fixes mapbox/carto#288
Merge pull request #289 from javisantana/master

fixes mapbox/carto#288
Test for #288 to keep it closed, space before zoom bug
add currently failing test for #290
Add test/rendering-mss/npm-debug.log to .gitignore
More tests for attachement (cf #245)
Merge pull request #292 from yohanboniface/attachment-tests

Attachment tests (cf #245)