Changelog for underscore fix, prepare to publish (#142)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf18c3f..b87c5b6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,6 @@
-## 1.5.4-dev
+## 1.5.4
 
+* Fix a bug with option names containing underscores.
 * Point towards `CommandRunner` in the docs for `ArgParser.addCommand` since it
   is what most authors will want to use instead.
 
diff --git a/pubspec.yaml b/pubspec.yaml
index 6ebe018..b8b58d9 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: args
-version: 1.5.4-dev
+version: 1.5.4
 homepage: https://github.com/dart-lang/args
 description: >-
  Library for defining parsers for parsing raw command-line arguments into a set