chore: delete travis configuration

.travis.yml

-language: php
-
-sudo: false
-
-php:
-  - 7.0
-
-before_script:
-  - sh -c "composer require 'cakephp/cakephp-codesniffer:dev-master'"
-  - phpenv rehash
-
-script:
-  - sh -c "vendor/bin/phpcs -p --extensions=php --standard=vendor/cakephp/cakephp-codesniffer/CakePHP ./src ./tests ./config ./webroot"
-
-notifications:
-  email: false