chore: workaround travis npm i issue

Author: pemrouz

.travis.yml

@@ -2,5 +2,7 @@ sudo: false
 language: node_js
 node_js:
   - "stable"
+before_install:
+  - npm i rijs@0.6.4-shrinkwrap
 
 after_script: NODE_ENV=test istanbul cover ./node_modules/mocha/bin/_mocha --report lcovonly -- -R spec && cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js && rm -rf ./coverage