Leaky ReLU

Implemented the Leaky ReLU unit described in this paper

Maas, Andrew L., Awni Y. Hannun, and Andrew Y. Ng. "Rectifier nonlinearities improve neural network acoustic models." ICML Workshop on Deep Learning for Audio, Speech, and Language Processing. 2013.

which shares similar sparse activation properties with the ReLU, but was shown easier to optimize.
I think the value of the relu_param isn't actually being used here because you define it after using the layer is constructed (in the line before, 84).