Make sure we test with both 2.0 and 1.9 of client-common

Author: Nyholm

.travis.yml

@@ -28,9 +28,11 @@ matrix:
     include:
         - php: 5.4
           env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true TEST_COMMAND="composer test-ci"
+        - php: 7.2
+          env: DEPENDENCIES="php-http/client-common:^1.9"
 
 before_install:
-    - travis_retry composer self-update
+    - if ! [ -z "$DEPENDENCIES" ]; then composer require --no-update ${DEPENDENCIES}; fi;
 
 install:
     - travis_retry composer update ${COMPOSER_FLAGS} --prefer-dist --no-interaction