Auto merge of servo#216 - Eijebong:itoa, r=nox

Update itoa to 0.4 and bump version

<!-- Reviewable:start -->
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/rust-cssparser/216)
<!-- Reviewable:end -->

Author: bors-servo

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cssparser"
-version = "0.23.2"
+version = "0.23.3"
 authors = [ "Simon Sapin <simon.sapin@exyr.org>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"
@@ -22,7 +22,7 @@ encoding_rs = "0.7"
 cssparser-macros = {path = "./macros", version = "0.3"}
 dtoa-short = "0.3"
 heapsize = {version = ">= 0.3, < 0.5", optional = true}
-itoa = "0.3"
+itoa = "0.4"
 matches = "0.1"
 phf = "0.7"
 procedural-masquerade = {path = "./procedural-masquerade", version = "0.1"}