Time for 1.0 (#18)

* Update CHANGELOG.md

* Update README.md

* Update pubspec.yaml
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6e104f9..b8a7dce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,8 @@
 # Changelog
 
-## 0.5.1
+## 1.0.0
 
+* Core APIs deemed stable; package version set to 1.0.0.
 * Added `split` methods on `Characters` and `CharacterRange`.
 
 ## 0.5.0
diff --git a/README.md b/README.md
index 8cb756a..cfaa988 100644
--- a/README.md
+++ b/README.md
@@ -1,8 +1,6 @@
 [![pub package](https://img.shields.io/pub/v/characters.svg)](https://pub.dev/packages/characters)
 [![Build Status](https://travis-ci.org/dart-lang/characters.svg?branch=master)](https://travis-ci.org/dart-lang/characters)
 
-**NOTE**: This package is in technical preview, and breaking API changes are to be expected.
-
 `Characters` are strings viewed as sequences of *user-perceived character*s,
 also know as [Unicode (extended) grapheme clusters](https://unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries).
 
diff --git a/pubspec.yaml b/pubspec.yaml
index c3072ad..8863486 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: characters
-version: 0.5.1
+version: 1.0.0
 description: String replacement with operations that are Unicode/grapheme cluster aware.
 homepage: https://www.github.com/dart-lang/characters