Update min SDK to 2.4 (#24)

Related to https://github.com/dart-lang/test/issues/1141
diff --git a/.travis.yml b/.travis.yml
index e9ef0bf..1c702c8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,6 @@
 language: dart
 dart:
-  - 2.3.0
+  - 2.4.0
   - dev
 
 dart_task:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index bd426fe..f6f0c0d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 1.1.7-dev
+
+* Update min Dart SDK to `2.4.0`.
+
 ## 1.1.6
 
 * Set max SDK version to `<3.0.0`, and adjust other dependencies.
diff --git a/pubspec.yaml b/pubspec.yaml
index 94646ae..1a4cd2c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: typed_data
-version: 1.1.6
+version: 1.1.7-dev
 
 description: >-
   Utility functions and classes related to the dart:typed_data library.
@@ -7,7 +7,7 @@
 homepage: https://github.com/dart-lang/typed_data
 
 environment:
-  sdk: '>=2.3.0 <3.0.0'
+  sdk: '>=2.4.0 <3.0.0'
 
 dev_dependencies:
   pedantic: ^1.0.0