update travis.yml file

Author: mhdcodes

.travis.yml

@@ -1,13 +1,11 @@
 language: php
 php:
-  - '7.0'
-  - '7.1'
-  - '7.2'
+  - "7.2"
 
 cache:
   directories:
     - $HOME/.composer/cache
 
 before_script:
-    - composer install
+  - composer install
 script: composer test

composer.json

@@ -15,7 +15,7 @@
         }
     ],
     "require": {
-        "php": ">=5.6"
+        "php": ">=7.2"
     },
     "require-dev": {
         "phpunit/phpunit": "5.7",