Minor adjustment on travis.

Author: byjg

.travis.yml

@@ -10,13 +10,14 @@ addons:
     - redis-container
 
 php:
+  - "7.3"
   - "7.2"
   - "7.1"
   - "7.0"
   - "5.6"
 
 before_install:
-  - echo "extension = memcached.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
+  - pecl install memcached
   - echo "extension = redis.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
 
 install: