Attempt to test multiple laravel versions with travis

.travis.yml

@@ -9,6 +9,26 @@ cache:
   directories:
     - $HOME/.composer/cache
 
+env:
+  - ILLUMINATE_VERSION=5.3.*
+
+matrix:
+  include:
+    - php: 5.6
+      env: ILLUMINATE_VERSION=5.3.*
+    - php: 7.0
+      env: ILLUMINATE_VERSION=5.3.*
+    - php: 7.1
+      env: ILLUMINATE_VERSION=5.3.*
+    - php: 5.6
+      env: ILLUMINATE_VERSION=5.4.*
+    - php: 7.0
+      env: ILLUMINATE_VERSION=5.4.*
+    - php: 7.1
+      env: ILLUMINATE_VERSION=5.4.*
+
 before_script:
-  - travis_retry composer update ${COMPOSER_FLAGS} --no-interaction --prefer-dist
-  - composer dumpautoload -o
+  - composer require "illuminate/support:${ILLUMINATE_VERSION}" --no-update
+  - composer require "illuminate/database:${ILLUMINATE_VERSION}" --no-update
+  - composer update ${COMPOSER_FLAGS} --no-interaction --prefer-dist
+  - composer dumpautoload -o