Update Symfony documentation (4.0.3)

Author: Thibaut

lib/docs/scrapers/symfony.rb

@@ -26,8 +26,18 @@ class Symfony < UrlScraper
       Licensed under the MIT License.
     HTML
 
+    version '4.0' do
+      self.release = '4.0.3'
+      self.base_url = "http://api.symfony.com/#{version}/"
+    end
+
+    version '3.4' do
+      self.release = '3.4.3'
+      self.base_url = "http://api.symfony.com/#{version}/"
+    end
+
     version '3.3' do
-      self.release = '3.3.10'
+      self.release = '3.3.15'
       self.base_url = "http://api.symfony.com/#{version}/"
     end