travis: simplify build matrix

Author: JanTvrdik

.travis.yml

@@ -5,36 +5,21 @@ php:
   - 7.2
   - master
 
+env:
+  - dependencies=lowest
+  - dependencies=highest
+
 matrix:
-  include:
-    - php: 7.0
-      env: dependencies=lowest
-    - php: 7.0
-      env: dependencies=highest
-    - php: 7.1
-      env: dependencies=lowest
-    - php: 7.1
-      env: dependencies=highest
-    - php: 7.2
-      env: dependencies=lowest
-    - php: 7.2
-      env: dependencies=highest
-    - php: master
-      env: dependencies=lowest
-    - php: master
-      env: dependencies=highest
   allow_failures:
-    - php: master
     - php: master
       env: dependencies=lowest
     - php: master
       env: dependencies=highest
 
 before_script:
   - composer self-update
-  - if [ -z "$dependencies" ]; then composer install; fi;
-  - if [ "$dependencies" = "lowest" ]; then composer update --prefer-lowest -n; fi;
-  - if [ "$dependencies" = "highest" ]; then composer update -n; fi;
+  - if [ "$dependencies" = "lowest" ]; then composer update --prefer-lowest --no-interaction; fi;
+  - if [ "$dependencies" = "highest" ]; then composer update --no-interaction; fi;
 
 script:
   - vendor/bin/phing