Multiple Guzzle versions on Travis

Author: soullivaneuh

.travis.yml

@@ -7,12 +7,19 @@ php:
   - 7.0
   - hhvm
 
+matrix:
+  fast_finish: true
+  include:
+    - php: 5.6
+      env: GUZZLE_VERSION=4.*
+
 before_install:
   # start a web server on port 8080, running in the background
   - bin/start_server.sh
 
 before_script:
   - composer self-update
+  - if [ "$GUZZLE_VERSION" != "" ]; then composer require "guzzlehttp/guzzle:${GUZZLE_VERSION}" --no-update; fi;
   - composer install --prefer-source
   - export LANG=C
   - export PATH=vendor/bin:$PATH