Update TravisCI config

.travis.yml

@@ -1,21 +1,37 @@
 language: php
 
+sudo: false
+
 php:
   - 5.6
   - 7.0
   - 7.1
 
 env:
-  matrix:
-    - COMPOSER_FLAGS="--prefer-lowest"
-    - COMPOSER_FLAGS=""
+  global:
+    - setup=stable
+    - coverage=no
 
 before_script:
-  - travis_retry composer self-update
-  - travis_retry composer update ${COMPOSER_FLAGS} --no-interaction --prefer-source
+  - composer config discard-changes true
+  - if [[ $setup = 'stable' ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable; fi
+  - if [[ $setup = 'coveralls' ]]; then travis_retry composer require "satooshi/php-coveralls=~0.7" --prefer-dist --no-interaction --dev; fi
 
 script:
-  - vendor/bin/phpunit --coverage-text --coverage-clover=coverage.clover
+  - if [[ $coverage = 'yes' ]]; then ./vendor/bin/phpunit --coverage-clover build/logs/clover.xml; fi
+  - if [[ $coverage = 'no' ]]; then ./vendor/bin/phpunit; fi
 
 after_script:
-  - php vendor/bin/ocular code-coverage:upload --format=php-clover coverage.clover
+  - if [[ $setup = 'coveralls' ]]; then php vendor/bin/coveralls -v; fi
+
+matrix:
+  include:
+    - php: 5.6
+      env: setup=coveralls coverage=yes
+    - php: 7.0
+      env: setup=coveralls coverage=yes
+    - php: 7.1
+      env: setup=coveralls coverage=yes
+  allow_failures:
+    - env: setup=coveralls coverage=yes
+  fast_finish: true