Revert "Allow dev to fail on travis (#71)" (#72)

This reverts commit 3b8d74b7ef408701c09a11470030f4316a59f005.
diff --git a/.travis.yml b/.travis.yml
index 0881a31..e110e4e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,6 +4,3 @@
   - stable
   - dev
 script: ./tool/travis.sh
-matrix:
-  allow_failures:
-    - dart: dev