Update smallvec to 0.6 and bump version

Author: Eijebong

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cssparser"
-version = "0.23.1"
+version = "0.23.2"
 authors = [ "Simon Sapin <[email protected]>" ]
 
 description = "Rust implementation of CSS Syntax Level 3"
@@ -27,7 +27,7 @@ matches = "0.1"
 phf = "0.7"
 procedural-masquerade = {path = "./procedural-masquerade", version = "0.1"}
 serde = {version = "1.0", optional = true}
-smallvec = "0.4.3"
+smallvec = "0.6"
 
 [build-dependencies]
 syn = "0.11"