build(semantic release): Adjust travis file to fix semantic release

Author: maxnussbaum

.travis.yml

@@ -15,7 +15,7 @@ before_install:
 
 install:
   - pip install --user bumpversion
-  - npm install @semantic-release/exec
+  - npm install -g @semantic-release/exec
   - bundle install
 
 script:
@@ -24,6 +24,9 @@ script:
 deploy:
   - provider: script
     script: npx travis-deploy-once "npx semantic-release"
+    on:
+      branch: master
+      rvm: 2.5.1
 
   - provider: rubygems
     api_key: $RUBYGEMS_API_KEY