Update readme
Update commander to 2.3.x.
Merge pull request #319 from aymericbeaumet/master

Updates readme with metalsmith's plugin info.
Merge pull request #320 from XhmikosR/commander

Updates commander to 2.3.x.
Turns comma splitter into a more generic splitter.

* No longer accepts splitted value as constructor argument but in split method instead.
* Accepts separator value to split over in constructor.
Fixes #316 - incorrect background processing.

* Reworks advanced processing for backgrounds so all properties are correctly identified.
* Fixes removing `0 0` background-position as it's default.
Adds `background` normalization according to W3C spec.
Removes `fourBySpacesOrFunctions` thanks to new Splitter helper.
Version 2.2.9.
Update browserify to v5.x.
Merge pull request #324 from XhmikosR/browserify

Update browserify to v5.x.
Fixes #325 - removing invalid special declarations.
Fixes #323 - variable references being stripped out.

* Advanced optimizations haven't supported CSS variables.
Improves performance of advanced mode validators.
Fixes #307 - background-color in muliple backgrounds.

Apparently multiple backgrounds allow background-color in last value only:
http://www.w3.org/TR/css3-background/#the-background
Fixes #322 - adds background-size support to advanced optimizer.
Version 2.2.10.
Fixes #326 - regression issue in background-size minification.
Version 2.2.11.
Fixes issue with tokenizer removing first selector after an unknown @ rule.

See discussion in #325.