Add release notes for 0.2.0

Author: cuviper

RELEASES.md

@@ -1,3 +1,45 @@
+# Release 0.2.0 (pending)
+
+All items exported from `num-integer`, `num-iter`, and `num-traits` are still
+semver-compatible with those exported by `num` 0.1.  If you have these as public
+dependencies in your own crates, it is not a breaking change to move to `num`
+0.2.  However, this is not true of `num-bigint`, `num-complex`, or
+`num-rational`, as those exported items are distinct in this release.
+
+A few common changes are listed below, but most of the development happens in
+the individual sub-crates.  Please consult their release notes for more details
+about recent changes:
+[`num-bigint`](https://github.com/rust-num/num-bigint/blob/master/RELEASES.md),
+[`num-complex`](https://github.com/rust-num/num-complex/blob/master/RELEASES.md),
+[`num-integer`](https://github.com/rust-num/num-integer/blob/master/RELEASES.md),
+[`num-iter`](https://github.com/rust-num/num-iter/blob/master/RELEASES.md),
+[`num-rational`](https://github.com/rust-num/num-rational/blob/master/RELEASES.md),
+and [`num-traits`](https://github.com/rust-num/num-traits/blob/master/RELEASES.md).
+
+### Enhancements
+
+- Updates to `num-integer`, `num-iter`, and `num-traits` are still compatible
+  with `num` 0.1.
+- 128-bit integers are supported with Rust 1.26 and later.
+- `BigInt`, `BigUint`, `Complex`, and `Ratio` all implement `Sum` and `Product`.
+
+### Breaking Changes
+
+- `num` now requires rustc 1.15 or greater.
+- `num-bigint`, `num-complex`, and `num-rational` have all been updated to 0.2.
+- It's no longer possible to toggle individual `num-*` sub-crates using cargo
+  features.  If you need that control, please use those crates directly.
+- There is now a `std` feature, enabled by default, along with the implication
+  that building *without* this feature makes this a `#![no_std]` crate.
+  `num::bigint` is not available without `std`, and the other sub-crates may
+  have limited functionality.
+- The `serde` dependency has been updated to 1.0, still disabled by default.
+  The `rustc-serialize` crate is no longer supported by `num`.
+- The `rand` dependency has been updated to 0.5, now disabled by default.  This
+  requires rustc 1.22 or greater for `rand`'s own requirement.
+
+**Contributors**: @CAD97, @cuviper, and the many sub-crate contributors!
+
 # Release 0.1.42 (2018-02-08)
 
 - [All of the num sub-crates now have their own source repositories][num-356].