Add PHP 7.4 Travis build

Also replace mock-objects with PHP 5.6-7.4 compatible fork sminnee/phpunit-mock-objects

Author: OndraM

.travis.yml

@@ -8,6 +8,7 @@ php:
   - '7.1'
   - '7.2'
   - '7.3'
+  - '7.4snapshot'
 
 env:
   global:
@@ -47,7 +48,7 @@ matrix:
 
     # Firefox with Geckodriver (W3C mode) inside Travis environment
     - name: 'Firefox latest on Travis (W3C protocol); no Selenium server'
-      php: 7.3
+      php: '7.3'
       env:
         - BROWSER_NAME="firefox"
         - GECKODRIVER="1"

composer.json

@@ -13,21 +13,22 @@
   "minimum-stability": "beta",
   "require": {
     "php": "^5.6 || ~7.0",
-    "symfony/process": "^2.8 || ^3.1 || ^4.0 || ^5.0",
-    "symfony/polyfill-mbstring": "^1.12",
     "ext-curl": "*",
+    "ext-json": "*",
     "ext-zip": "*",
-    "ext-json": "*"
+    "symfony/polyfill-mbstring": "^1.12",
+    "symfony/process": "^2.8 || ^3.1 || ^4.0 || ^5.0"
   },
   "require-dev": {
+    "friendsofphp/php-cs-fixer": "^2.0",
+    "jakub-onderka/php-parallel-lint": "^0.9.2",
+    "php-coveralls/php-coveralls": "^2.0",
+    "php-mock/php-mock-phpunit": "^1.1",
     "phpunit/phpunit": "^5.7",
     "sebastian/environment": "^1.3.4 || ^2.0 || ^3.0",
-    "friendsofphp/php-cs-fixer": "^2.0",
+    "sminnee/phpunit-mock-objects": "^3.4",
     "squizlabs/php_codesniffer": "^2.6",
-    "php-mock/php-mock-phpunit": "^1.1",
-    "php-coveralls/php-coveralls": "^2.0",
-    "symfony/var-dumper": "^3.3 || ^4.0 || ^5.0",
-    "jakub-onderka/php-parallel-lint": "^0.9.2"
+    "symfony/var-dumper": "^3.3 || ^4.0 || ^5.0"
   },
   "suggest": {
     "ext-SimpleXML": "For Firefox profile creation"
@@ -57,6 +58,9 @@
       "vendor/bin/phpstan.phar analyze ./lib ./tests --level 2 -c phpstan.neon --ansi"
     ]
   },
+  "config": {
+    "sort-packages": true
+  },
   "extra": {
     "branch-alias": {
       "dev-community": "1.8.x-dev"