fix(tests): scope the addition of each engine to only core

Author: bmuenzenmeyer

.travis.yml

@@ -6,12 +6,12 @@ before_install:
 before_script:
   - npm install -g [email protected]
   - npm run bootstrap
-  - lerna add @pattern-lab/engine-mustache
-  - lerna add @pattern-lab/engine-handlebars
-  - lerna add @pattern-lab/engine-underscore
-  - lerna add @pattern-lab/engine-liquid
-  - lerna add @pattern-lab/engine-twig
-  - lerna add @pattern-lab/engine-react
+  - lerna add @pattern-lab/engine-mustache --scope=@pattern-lab/core
+  - lerna add @pattern-lab/engine-handlebars --scope=@pattern-lab/core
+  - lerna add @pattern-lab/engine-underscore --scope=@pattern-lab/core
+  - lerna add @pattern-lab/engine-liquid --scope=@pattern-lab/core
+  - lerna add @pattern-lab/engine-twig --scope=@pattern-lab/core
+  - lerna add @pattern-lab/engine-react --scope=@pattern-lab/core
 
 branches:
   only: