Revert "Deprecate PHP 7.1" (drupal-composer#521)

This reverts commit 5085410.

Author: webflo

.travis.yml

@@ -3,6 +3,8 @@ dist: trusty
 sudo: false
 
 php:
+  - 7.0
+  - 7.1
   - 7.2
   - 7.3
 

README.md

@@ -132,14 +132,14 @@ Follow the instructions in the [documentation on drupal.org](https://www.drupal.
 
 ### How do I specify a PHP version ?
 
-This project supports PHP 7.2 as minimum version (see [Drupal 8 PHP requirements](https://www.drupal.org/docs/8/system-requirements/drupal-8-php-requirements)).
+This project supports PHP 5.6 as minimum version (see [Drupal 8 PHP requirements](https://www.drupal.org/docs/8/system-requirements/drupal-8-php-requirements)), however it's possible that a `composer update` will upgrade some package that will then require PHP 7+.
 
-You can add this code to specify the PHP version you want to use in the `config` section of `composer.json`:
+To prevent this you can add this code to specify the PHP version you want to use in the `config` section of `composer.json`:
 ```json
 "config": {
     "sort-packages": true,
     "platform": {
-        "php": "7.3.9"
+        "php": "5.6.40"
     }
 },
 ```

composer.json

@@ -16,7 +16,7 @@
         }
     ],
     "require": {
-        "php": ">=7.2",
+        "php": ">=5.6",
         "composer/installers": "^1.2",
         "cweagans/composer-patches": "^1.6.5",
         "drupal-composer/drupal-scaffold": "^2.5",