fix: typo correction in travis.yml (#249)

after_sucess -> after_success
Travis docs: https://docs.travis-ci.com/user/job-lifecycle/

Author: trivikr

.travis.yml

@@ -6,5 +6,5 @@ install:
   - npm run bootstrap
 script:
   - npm run test
-after_sucess:
+after_success:
   - ./node_modules/.bin/codecov -f coverage/*.json