Auto merge of #58 - mbrubeck:bump, r=jdm

Release version 0.4.2.

* Add `SmallVec::from_buf` constructor (#56).
* Add optional `serde` (de-)serialization support (#57).

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Author: bors-servo

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "smallvec"
-version = "0.4.1"
+version = "0.4.2"
 authors = ["Simon Sapin <simon.sapin@exyr.org>"]
 license = "MPL-2.0"
 repository = "https://github.com/servo/rust-smallvec"