remove warn, add assert
remove warn, add assert

ufal/neuralmonkey,juliakreutzer/bandit-neuralmonkey,bastings/neuralmonkey,juliakreutzer/bandit-neuralmonkey,ufal/neuralmonkey,bastings/neuralmonkey,bastings/neuralmonkey,juliakreutzer/bandit-neuralmonkey,ufal/neuralmonkey,juliakreutzer/bandit-neuralmonkey,bastings/neuralmonkey,ufal/neuralmonkey,ufal/neuralmonkey,bastings/neuralmonkey,juliakreutzer/bandit-neuralmonkey