travis: test npm-publish latest and bleedingedge versions

.travis.yml

@@ -10,3 +10,11 @@ install:
   - cd external/amber-cli
   - npm install
   - cd ../..
+script:
+  - npm test
+  - cd external/amber-cli
+  - npm install -g amber-cli
+  - AMBER_CLI=amber npm test
+  - npm install -g amber-cli@bleedingedge
+  - AMBER_CLI=amber npm test
+  - cd ../..