v1.5.3

• Use late static binding for config classes #25
• Remove Doctrine from dependencies (add Doctrine and Propel as suggestions) #35
• Add relative option for PublishAssetsTask #43
• Add an option to test:all task to show full output #55
• Improve PHP built-in webserver compatibility #58
• Update Swiftmailer to ~5.2.1 #59
• Re-add Propel in sfDatabaseSessionStorage #66