Update security.rst

Correct file path mentioned in comment
Added translation cookbooks about session
Merge pull request #527 from symfony-fr/2.4

Merging 2.4
Merge pull request #524 from TNT-razor/patch-1

Update security.rst (Correct file path mentioned in comment)
Merge pull request #525 from saro0h/session

Added translation cookbooks about session
Merge branch 'master', remote-tracking branch 'origin'