Add PHP 7.1 to travis, remove HHVM

.travis.yml

@@ -4,12 +4,11 @@ php:
   - '5.5'
   - '5.6'
   - '7.0'
-  - hhvm
+  - '7.1'
   - nightly
 
 matrix:
   allow_failures:
-    - php: hhvm
     - php: nightly
 
 
@@ -19,8 +18,6 @@ before_script:
 script:
   - vendor/bin/phpunit --coverage-clover=coverage.clover
 
-
-# only send coverage for PHP 5.6
 after_script:
   - wget https://scrutinizer-ci.com/ocular.phar
   - php ocular.phar code-coverage:upload --format=php-clover coverage.clover