Version 0.6.3

Changes in this release:

* Fix possible double-free in `insert_many` when passed an iterator that
  panics in `next` (servo#103)
* Add a new `union` feature (disabled by default) that reduces the size
  of the SmallVec struct (servo#94)
* Improve performance of `extend` and `from_elem` (servo#93)
* Improve performance of `drop` (servo#100)
* Update dev-dependency on `bincode` (servo#102)
* Update to build without `std` on current Rust nightly (servo#104)
* Additional benchmarks (servo#95, servo#97).

Author: mbrubeck

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "smallvec"
-version = "0.6.1"
+version = "0.6.3"
 authors = ["Simon Sapin <[email protected]>"]
 license = "MIT/Apache-2.0"
 repository = "https://github.com/servo/rust-smallvec"