[ci] install deps before deploying the documentation

Author: scottinet

.travis.yml

@@ -103,6 +103,7 @@ jobs:
 
       install:
         - pip install awscli --upgrade --user
+        - npm ci
 
       script:
         - npm run doc-prepare
@@ -135,6 +136,7 @@ jobs:
 
       install:
         - pip install awscli --upgrade --user
+        - npm ci
 
       script:
         - npm run doc-prepare