Use the latest Composer to make Puli work

Author: mnapoli

.travis.yml

@@ -12,6 +12,7 @@ matrix:
       env: dependencies=lowest
 
 before_script:
+  - composer selfupdate
   - if [[ "$TRAVIS_PHP_VERSION" == '5.6' ]]; then composer require satooshi/php-coveralls:dev-master -n ; fi
   - if [[ "$TRAVIS_PHP_VERSION" != '5.6' ]]; then composer install -n ; fi
   - if [ "$dependencies" = "lowest" ]; then composer update --prefer-lowest --prefer-stable -n; fi;