fix(travis): simplify build steps

speed up build by installing dependencies only once

Author: bermanboris

.travis.yml

@@ -1,8 +1,5 @@
 language: node_js
 
-install:
-  - yarn
-
 cache: yarn
 
 node_js:
@@ -18,24 +15,20 @@ stages:
 
 jobs:
   include:
-    - stage: test
-      install:
-        - yarn install
-      script:
-        - yarn test:prod
+    - stage: install
+      script: yarn install
+      skip_cleanup: true
+
+      - stage: test
+      script: yarn test:prod
+      skip_cleanup: true
 
     - stage: build
-      install:
-        - yarn install
-      script:
-        - yarn build
+      script: yarn build
 
     - stage: release
-      # Advanced: optionally overwrite your default `script` step to skip the tests
-      # script: skip
       deploy:
         provider: script
         skip_cleanup: true
         script:
-          - yarn build
           - yarn semantic-release