Test on PHP 7.1 (#36)

* Test on PHP 7.1

* Update .travis.yml

Author: GrahamCampbell

.travis.yml

@@ -11,6 +11,7 @@ php:
     - 5.5
     - 5.6
     - 7.0
+    - 7.1
     - hhvm
 
 env:
@@ -28,7 +29,7 @@ matrix:
           env: COMPOSER_FLAGS="--prefer-stable --prefer-lowest" COVERAGE=true TEST_COMMAND="composer test-ci"
 
 before_install:
-    - if [[ $COVERAGE != true && $TRAVIS_PHP_VERSION != hhvm ]]; then phpenv config-rm xdebug.ini; fi
+    - if [[ $COVERAGE != true ]]; then phpenv config-rm xdebug.ini || true; fi
 
 install:
     # To be removed when this issue will be resolved: https://github.com/composer/composer/issues/5355