update symfony deps to 2.3
update symfony deps to 2.3

2.1 has been unsupported long enough.  Has anybody tested whether the 2.1 dep actually did work?
romainneutron/NelmioSecurityBundle,lyrixx/NelmioSecurityBundle,romainneutron/NelmioSecurityBundle,nelmio/NelmioSecurityBundle,stof/NelmioSecurityBundle