Update .travis.yml

Author: tommy-muehle

.travis.yml

@@ -11,17 +11,18 @@ matrix:
     - php: 5.6
     - php: hhvm
     - php: nightly
+    - php: 7.1
     - php: 7.0
       env: COVERAGE=yes
   allow_failures:
     - php: nightly
     - php: hhvm
   fast_finish: true
 before_install:
-  - if [[ $TRAVIS_PHP_VERSION != hhvm && $COVERAGE != yes ]]; then phpenv config-rm xdebug.ini; fi;
+  - if [[ $TRAVIS_PHP_VERSION != hhvm && $TRAVIS_PHP_VERSION != nightly && $COVERAGE != yes ]]; then phpenv config-rm xdebug.ini; fi;
   - composer selfupdate
 install:
-  - composer update --no-interaction --prefer-source
+  - composer update --no-interaction
 script:
   - ./bin/phpcs.phar --standard=PSR2 ./src -v
   - ./bin/phpcpd.phar ./src