Allow failures for Haxe dev builds on Travis (#351)

Author: Gama11

.travis.yml

@@ -16,3 +16,8 @@ script:
 after_success:
   - bash <(curl -s https://codecov.io/bash) || echo "Codecov did not collect coverage reports"
 sudo: false
+dist: trusty
+
+matrix:
+  allow_failures:
+    - haxe: development