Fix current php version requirement to current PHP LTS

IvanChepurnyi · IvanChepurnyi · commit 21ec0f867190 · 2018-05-22T23:06:10.000+02:00
diff --git a/composer.json b/composer.json
@@ -13,7 +13,7 @@
         }
     ],
     "require": {
-        "php": "^7.2",
+        "php": "^7.1",
         "markrogoyski/math-php": "^0.42.0"
     },
     "autoload": {
