Update the changelog for 2.1.0
Update the changelog for 2.1.0

Soullivaneuh/KnpMenuBundle,benji07/KnpMenuBundle,Soullivaneuh/KnpMenuBundle,KnpLabs/KnpMenuBundle,javiereguiluz/KnpMenuBundle,piotrantosik/KnpMenuBundle,stof/KnpMenuBundle