add changelog, prepare for 2.1.5 (#92)

CHANGELOG.md

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5cb220f..c7e6aff 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,8 @@
+## 2.1.5
+
+* Improve example and package description to address package site maintenance
+  suggestions.
+
 ## 2.1.4
   * BugFix: padding was incorrect for some SHA-512/328.
 

pubspec.yaml

diff --git a/pubspec.yaml b/pubspec.yaml
index 5359084..420fb87 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: crypto
-version: 2.1.5-dev
-description: Library of cryptographic functions.
+version: 2.1.5
+description: Implementations of SHA, MD5, and HMAC cryptographic functions
 homepage: https://www.github.com/dart-lang/crypto
 
 environment: