Mention collaborator Lullabot

Author: sabberworm

README.md

@@ -590,6 +590,7 @@ class Sabberworm\CSS\CSSList\Document#4 (2) {
 * [ju1ius](https://github.com/ju1ius) for the specificity parsing code and the ability to expand/compact shorthand properties.
 * [GaryJones](https://github.com/GaryJones) for lots of input and [http://css-specificity.info/](http://css-specificity.info/).
 * [ossinkine](https://github.com/ossinkine) for a 150 time performance boost.
+* [Lullabot](https://github.com/Lullabot) for a patch that allows to know the line number for each parsed token.
 * [docteurklein](https://github.com/docteurklein) for output formatting and `CSSList->remove()` inspiration.
 * [nicolopignatelli](https://github.com/nicolopignatelli) for PSR-0 compatibility.
 * [diegoembarcadero](https://github.com/diegoembarcadero) for keyframe at-rule parsing.