ICM: Made different Travis test envs more independent.

Author: dmitry-ivanov

Diff for: .travis.yml

@@ -12,7 +12,7 @@ before_install:
   - echo "extension = redis.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini
 
 install:
-  - composer install
+  - composer update
   - composer require satooshi/php-coveralls --dev
 
 script: