clean up travis config

.travis.yml

@@ -1,32 +1,20 @@
 language: php
 
-matrix:
-  include:
-    - php: 7.1
-      env:
-        - DEPS=lowest
-    - php: 7.1
-      env:
-        - DEPS=latest
-    - php: 7.2
-      env:
-        - DEPS=lowest
-    - php: 7.2
-      env:
-        - DEPS=latest
+php:
+  - 7.1
+  - 7.2
 
 before_script:
   - mkdir -p build/logs
   - composer self-update
-  - if [[ $DEPS == 'lowest' ]]; then travis_retry composer update --prefer-lowest --prefer-stable --no-interaction ; fi
-  - if [[ $DEPS == 'latest' ]]; then travis_retry composer install --prefer-source --no-interaction ; fi
+  - travis_retry composer install --prefer-source --no-interaction
   - composer global require --dev phpstan/phpstan
   - composer dump-autoload -o
 
 script:
   - ~/.composer/vendor/bin/phpstan analyse src/ --level=max
   - bin/kahlan --coverage=4 --reporter=verbose --clover=build/logs/clover.xml
-  - if [[ $DEPS == 'latest' ]]; then bin/php-coveralls -v --exclude-no-stmt ; fi
+  - bin/php-coveralls -v --exclude-no-stmt
 
 notifications:
     email: false