Fix conflicts, add RNN modules, PReLU and formatting

[egrinstein]

Hi there,

Thank you very much for this library, it has been very helpful in my research.

I wanted to share with you some modifications I made to the code which I hope you and the other users will find positive.

Firstly, the master branch in the library has some <<<<>>>> signs in the code, which I removed. I have also put the code through a formatter to increase its readability.

In terms of added functionality, I have included a naive implementation of the complex-valued GRU and LSTM. Finally, I have added a PReLU activation function, which is used here for example.

I hope I am being helpful. Please feel free to ask me for further modifications and clarifications.

Cheers,

Eric