0.4
* add a set module
* remove the rc and arc modules. There is no observable
performance difference between rc and arc, so just use arc
everywhere. This is especially relevant because all the practical
applications of this library than I know about require using Arc.
* BREAKING: fix return type of insert and remove to match BTreeMap

0.3.2
* fix a small performance regression in update_many caused by my last change

0.3.1(yanked)
* fix a bug in update_many that could rarely cause a removed item not to be removed

0.3.0
* BREAKING: change the name of insert_sorted to insert_many
* add update, and update_many
* insert 14% performance improvement
* insert_many 42% performance improvement on unsorted data, now faster than insert on random data

0.2.1
* BREAKING: change signature of insert to match BTreeMap as closely as possible. Sorry I was new to rust when I first wrote this module :-(

0.2.0
* iteration runs in constant space
* Implement collection range api
* Implement DoubleEndedIterator
* insert_sorted performance improved on degenerate cases
* BREAKING: insert_sorted now takes IntoIterator instead of an explicit slice
* BREAKING: change the name of length to len, like BTreeMap

0.1.2
Initial public release
