Prepare to publish 0.3.1
diff --git a/pubspec.yaml b/pubspec.yaml
index b2467e0..8c7c28c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,10 +1,10 @@
 name: tar
 description: Memory-efficient, streaming implementation of the tar file format
-version: 0.3.0
+version: 0.3.1
 repository: https://github.com/simolus3/tar/
 
 environment:
-  sdk: '>=2.12.0-29.10.beta <3.0.0'
+  sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
   chunked_stream: ^1.4.0