Add new php7.1 variants to Travis (via "update.sh")

Author: tianon

.travis.yml

@@ -8,6 +8,9 @@ env:
   - VARIANT=php7.0/apache
   - VARIANT=php7.0/fpm
   - VARIANT=php7.0/fpm-alpine
+  - VARIANT=php7.1/apache
+  - VARIANT=php7.1/fpm
+  - VARIANT=php7.1/fpm-alpine
 
 install:
   - git clone https://github.com/docker-library/official-images.git ~/official-images