added docstrings to sequence class and remove useless feed dict implementation
added docstrings to sequence class and remove useless feed dict implementation

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