Updated Travis configuration to allow packages to be tested in parallel jobs (dart-lang/yaml_edit#59)

pkgs/yaml_edit/mono_pkg.yaml

diff --git a/pkgs/yaml_edit/mono_pkg.yaml b/pkgs/yaml_edit/mono_pkg.yaml
index db15a21..a1ac6a4 100644
--- a/pkgs/yaml_edit/mono_pkg.yaml
+++ b/pkgs/yaml_edit/mono_pkg.yaml
@@ -1,8 +1,10 @@
 dart:
-- stable
+  - stable
+  - dev
+
 stages:
-- analyze:
-  - dartanalyzer
-  - dartfmt
-- tests:
-  - test
+  - analyze:
+      - dartanalyzer
+      - dartfmt
+  - tests:
+      - test