Prepare to release 0.5.13 (#53)

diff --git a/pubspec.yaml b/pubspec.yaml
index 8b8cdb7..6783367 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: dart2js_info
-version: 0.5.13-dev
+version: 0.5.13
 
 description: >
   Libraries and tools to process data produced when running dart2js with