[BUGFIX] Adjust version number in condition

Follow-up to #114

Author: Stefano Kowalke

.travis.yml

@@ -42,7 +42,7 @@ before_script:
         pecl install igbinary > /dev/null;
     fi
   - >
-    if [[ "$TRAVIS_PHP_VERSION" == "5.5" || "$TRAVIS_PHP_VERSION" == "5.5"]]; then
+    if [[ "$TRAVIS_PHP_VERSION" == "5.5" || "$TRAVIS_PHP_VERSION" == "5.6"]]; then
       echo "extension = memcache.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini;
       echo "extension = redis.so" >> ~/.phpenv/versions/$(phpenv version-name)/etc/php.ini;
     fi