Update composer dependencies

.ci/docker_install.sh

-#!/bin/bash
-
-[[ ! -e /.dockerenv ]] && [[ ! -e /.dockerinit ]] && exit 0
-
-set -xe
-
-apt-get update
-apt-get install -qyy git unzip curl
-
-# Python tools to run the test HTTP API
-apt-get install -qyy python-pip gunicorn
-pip install httpbin
-
-curl --location --output /usr/local/bin/phpunit https://phar.phpunit.de/phpunit.phar
-chmod +x /usr/local/bin/phpunit
-
-curl --location --output /usr/local/bin/composer https://getcomposer.org/composer.phar
-chmod +x /usr/local/bin/composer
-
-echo "date.timezone = UTC" >> /usr/local/etc/php/conf.d/test.ini
-
-pecl install xdebug
-docker-php-ext-enable xdebug

.gitlab-ci.yml

 test:5.6:
   image: 1of0/php-ci:5.6-httpbin
   script:
-  - composer install
-  - phpunit --configuration phpunit.xml
+  - composer install --ignore-platform-reqs
+  - vendor/bin/phpunit --configuration phpunit.xml
 
 test:7.0:
   image: 1of0/php-ci:7.0-httpbin
   script:
-  - composer install
-  - phpunit --configuration phpunit.xml
+  - composer install --ignore-platform-reqs
+  - vendor/bin/phpunit --configuration phpunit.xml
 
 coverage:
   image: 1of0/php-ci:7.0-httpbin
   script:
-  - composer install
-  - phpunit --coverage-text --colors=never --configuration phpunit.xml
+  - composer install --ignore-platform-reqs
+  - vendor/bin/phpunit --coverage-text --colors=never --configuration phpunit.xml