Update README with large file guidelines
Update README with large file guidelines

Fixes #158

Former-commit-id: 2a81ba351f050c369fe071fb14aa75c336cc3990
masteinhauser/devopsdays-web,joelaha/devopsdays-web,benjohnson77/devopsdays-web,joelaha/devopsdays-web,benjohnson77/devopsdays-web,benjohnson77/devopsdays-web,masteinhauser/devopsdays-web,joelaha/devopsdays-web,joelaha/devopsdays-web,masteinhauser/devopsdays-web,masteinhauser/devopsdays-web,benjohnson77/devopsdays-web