reenable mongo

.travis.yml

@@ -11,12 +11,14 @@ php:
 matrix:
   fast_finish: true
   allow_failures:
+    - php: 7.0
     - php: hhvm
 
 services:
   - mongodb
 
 before_script:
+  - echo "extension = mongo.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
   - travis_retry composer self-update
   - travis_retry composer install --no-interaction --prefer-source
   - if [[ "$TRAVIS_PHP_VERSION" == '5.6' ]]; then travis_retry composer require satooshi/php-coveralls:dev-master --no-interaction ; fi