[ci skip] Section about attention visualization
[ci skip] Section about attention visualization

Add a section about attention in visualization.rst (#141)
ufal/neuralmonkey,juliakreutzer/bandit-neuralmonkey,juliakreutzer/bandit-neuralmonkey,juliakreutzer/bandit-neuralmonkey,bastings/neuralmonkey,ufal/neuralmonkey,bastings/neuralmonkey,juliakreutzer/bandit-neuralmonkey,bastings/neuralmonkey,bastings/neuralmonkey,ufal/neuralmonkey,juliakreutzer/bandit-neuralmonkey,ufal/neuralmonkey,ufal/neuralmonkey,bastings/neuralmonkey