Removing php7.1 for now, and reverting composer.json mcrypt requirement

.travis.yml

@@ -3,7 +3,6 @@ php:
   - 5.5
   - 5.6
   - 7.0
-  - 7.1
 before_script:
   - composer install
 script: vendor/bin/phpunit

composer.json

@@ -21,6 +21,7 @@
     ],
     "require": {
         "php": ">=5.5.0",
+        "ext-mcrypt": "*",
 		"sarciszewski/php-future": "0.4.*"
     },
     "require-dev": {