Implementation Request: dropout between gates in LSTM

[supakjk]

http://arxiv.org/abs/1512.05287 shows the usage of dropout between gates in LSTM. It would be great if we can also easily use such "inside" dropouts in rnn modules like FastLSTM.
Keras already supports it https://keras.io/layers/recurrent/

[jnhwkim]

@supakjk bayesian dropout on GRU is implemented but yet to LSTM. However, I've already implemented it recently for my experiment. When the test is done, I'll send a PR including testcases.

[supakjk]

It would also be great if we can easily set the initial forget gate bias.

[jnhwkim]

Can you check the implementation? You can use nn.LSTM or nn .FastLSTM .

You can access submodule via self.recurrentModule.

[jnhwkim]

Refer to #382.