Sync with php 7.3

Author: greg-md

.gitignore

@@ -1,2 +1,3 @@
 /vendor
 /coverage
+.phpunit.result.cache

.styleci.yml

@@ -6,3 +6,4 @@ enabled:
 disabled:
   - concat_without_spaces
   - simplified_null_return
+  - align_double_arrow

.travis.yml

@@ -1,7 +1,7 @@
 language: php
 
 php:
-  - '7.1'
+  - '7.3'
 
 install:
   composer install

composer.json

@@ -12,14 +12,14 @@
     { "name": "Grigorii Duca", "email": "contact@greg.md", "homepage": "http://greg.md/" }
   ],
   "require": {
-    "php": "^7.1",
+    "php": "^7.3",
     "ext-pdo": "*",
     "ext-ctype": "*",
     "ext-json": "*"
   },
   "require-dev": {
-    "phpunit/phpunit": "^7.4",
-    "symfony/var-dumper": "^4.1"
+    "phpunit/phpunit": "^8",
+    "symfony/var-dumper": "^4"
   },
   "autoload": {
     "psr-4": {