Bump SF4 stable tags and update project structure

Author: Tiago Brito

composer.json

@@ -2,13 +2,13 @@
  "name": "php-vcr/php-vcr",
  "description": "Record your test suite's HTTP interactions and replay them during future test runs for fast, deterministic, accurate tests.",
  "license": "MIT",
- 
+
  "scripts": {
  "test": "./vendor/bin/phpunit",
  "lint": "./vendor/bin/php-cs-fixer fix --verbose --diff --dry-run --config-file=.php_cs",
  "fix": "./vendor/bin/php-cs-fixer fix --verbose --diff --config-file=.php_cs"
  },
- 
+
  "authors": [
  {
  "name": "Adrian Philipp",
@@ -19,8 +19,8 @@
  "require": {
  "ext-curl": "*",
  "beberlei/assert": "^2.0",
- "symfony/yaml": "~2.1|^3.0",
- "symfony/event-dispatcher": "^2.4|^3.0"
+ "symfony/yaml": "~2.1|^3.0|^4.0",
+ "symfony/event-dispatcher": "^2.4|^3.0|^4.0"
  },
 
  "require-dev": {