Use environment variables since there's no way to pass secure data to deploy script provider

Author: dhui

Diff for: .travis.yml

@@ -11,6 +11,7 @@ env:
   global:
     - MIGRATE_TEST_CONTAINER_BOOT_TIMEOUT=60
     - DOCKER_USERNAME=golangmigrate
+    -   secure: "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"
 
 services:
   - docker
@@ -75,8 +76,6 @@ deploy:
       tags: true
   - provider: script
     script: ./docker-deploy.sh
-    token:
-      secure: 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
     on:
       go: "1.10.x"
       repo: golang-migrate/migrate