Bump the minimum Symfony version to 2.7
Bump the minimum Symfony version to 2.7

GawainLynch/bolt,lenvanessen/bolt,electrolinux/bolt,richardhinkamp/bolt,joshuan/bolt,richardhinkamp/bolt,rarila/bolt,hannesl/bolt,rossriley/bolt,electrolinux/bolt,Intendit/bolt,bolt/bolt,electrolinux/bolt,nikgo/bolt,electrolinux/bolt,richardhinkamp/bolt,winiceo/bolt,Raistlfiren/bolt,rossriley/bolt,hannesl/bolt,nantunes/bolt,lenvanessen/bolt,CarsonF/bolt,pygillier/bolt,Intendit/bolt,rossriley/bolt,HonzaMikula/masivnipostele,marcin-piela/bolt,HonzaMikula/masivnipostele,cdowdy/bolt,bolt/bolt,winiceo/bolt,romulo1984/bolt,hugin2005/bolt,kendoctor/bolt,hugin2005/bolt,tekjava/bolt,Eiskis/bolt-base,one988/cm,pygillier/bolt,tekjava/bolt,kendoctor/bolt,rarila/bolt,codesman/bolt,xeddmc/bolt,GawainLynch/bolt,joshuan/bolt,Eiskis/bolt-base,hugin2005/bolt,Raistlfiren/bolt,kendoctor/bolt,CarsonF/bolt,pygillier/bolt,codesman/bolt,Calinou/bolt,nantunes/bolt,richardhinkamp/bolt,marcin-piela/bolt,hannesl/bolt,Calinou/bolt,Calinou/bolt,joshuan/bolt,xeddmc/bolt,cdowdy/bolt,xeddmc/bolt,rarila/bolt,nikgo/bolt,winiceo/bolt,codesman/bolt,GawainLynch/bolt,bolt/bolt,nantunes/bolt,tekjava/bolt,joshuan/bolt,GawainLynch/bolt,one988/cm,cdowdy/bolt,hannesl/bolt,pygillier/bolt,winiceo/bolt,codesman/bolt,xeddmc/bolt,Intendit/bolt,tekjava/bolt,HonzaMikula/masivnipostele,nikgo/bolt,HonzaMikula/masivnipostele,rossriley/bolt,nantunes/bolt,Raistlfiren/bolt,marcin-piela/bolt,lenvanessen/bolt,nikgo/bolt,Calinou/bolt,kendoctor/bolt,one988/cm,romulo1984/bolt,one988/cm,Eiskis/bolt-base,bolt/bolt,cdowdy/bolt,CarsonF/bolt,marcin-piela/bolt,romulo1984/bolt,CarsonF/bolt,romulo1984/bolt,lenvanessen/bolt,Raistlfiren/bolt,hugin2005/bolt,Eiskis/bolt-base,rarila/bolt,Intendit/bolt