simplify conditions in img reader
simplify conditions in img reader

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