remove redundant builds, use both twig 2.4/1.3 for lower bound test

.travis.yml

@@ -2,49 +2,38 @@ language: php
 
 php:
   - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
+#  - 7.1
+#  - 7.2
+#  - 7.3
 
 sudo: false
 
 cache:
   directories:
     - $HOME/.composer/cache/files
 
-env:
-  - SYMFONY_VERSION=3.0.*
-
 matrix:
   fast_finish: true
   include:
-    - php: 7.2
-      env: SYMFONY_VERSION=3.3.*
-    - php: 7.2
-      env: SYMFONY_VERSION=3.4.*
-    - php: 7.2
-      env: SYMFONY_VERSION=4.0.*;ASSETIC=skip
-    - php: 7.2
-      env: SYMFONY_VERSION=4.1.*;ASSETIC=skip
-    - php: 7.2
-      env: SYMFONY_VERSION=@dev;ASSETIC=skip
-    - php: 7.3
-      env: SYMFONY_VERSION=3.3.*
-    - php: 7.3
-      env: SYMFONY_VERSION=3.4.*
-    - php: 7.3
-      env: SYMFONY_VERSION=4.0.*;ASSETIC=skip
-    - php: 7.3
-      env: SYMFONY_VERSION=4.1.*;ASSETIC=skip
-    - php: 7.3
-      env: SYMFONY_VERSION=@dev;ASSETIC=skip
+#    - php: 7.3
+#      env: SYMFONY_VERSION=3.4.*
+#    - php: 7.3
+#      env: SYMFONY_VERSION=4.2.*;ASSETIC=skip
+#    - php: 7.3
+#      env: SYMFONY_VERSION=4.3.*;ASSETIC=skip
+    - php: 7.0
+      env: SYMFONY_VERSION=3.0;COMPOSER_FLAGS="--prefer-dist --prefer-lowest";TWIG_VERSION=^2.4
     - php: 7.0
-      env: TWIG_VERSION=2.7.*
-    - php: 7.1
-      env: DEPENDENCIES=beta
-  allow_failures:
-    - php: 7.2
-      env: SYMFONY_VERSION=@dev;ASSETIC=skip
+      env: SYMFONY_VERSION=3.0;COMPOSER_FLAGS="--prefer-dist --prefer-lowest";TWIG_VERSION=^1.34
+#    - php: 7.3
+#      env: SYMFONY_VERSION=@dev;ASSETIC=skip
+#    - php: 7.3
+#      env: DEPENDENCIES=beta
+#  allow_failures:
+#    - php: 7.3
+#      env: SYMFONY_VERSION=@dev;ASSETIC=skip
+#    - php: 7.3
+#      env: DEPENDENCIES=beta
 
 before_install:
   - composer self-update
@@ -55,7 +44,4 @@ before_install:
 
 install: composer update --prefer-source $COMPOSER_FLAGS
 
-script: ./vendor/bin/phpunit --coverage-text
-
-notifications:
-  slack: liip:3QOs1QKt3aCFxpJvRzpJCbVZ
+script: ./vendor/bin/phpunit --coverage-text