Prepare for v1.0.0 release

[eyedol]

Add command for releasing via Travis CI. Add these

script:
  - ./gradlew build --no-daemon
  - if [ -n "$TRAVIS_TAG" ]; then ./gradlew build publishPlugins --no-daemon; fi
env:
  global:
  # GRADLE_PUBLISH_KEY
  - secure: <secure gradle publish key>
  # GRADLE_PUBLISH_SECRET
  - secure: <secure gradle screte key>

Setup credentials for publishing to Gradle plugin registry

Add Changelog file