Python 3 support, persistent RNN kernels, and improvements to dataloader, convolutional kernels and docs.

• Python2/Python3 compatibility [#191]
• Support for Pascal GPUs
• Persistent RNN kernels [#262]
• Implement Binarized Neural Networks from http://arxiv.org/pdf/1602.02830v3.pdf (added in v1.5.4)
• Dataloader enhancements (audio loader with examples)
• HDF5 file data iterator
• Convolution kernel improvements
• API documentation improvements [#234, #244, #263]
• Cache directory cleanup
• Reorganization of all unit tests
• Bug fixes [#182, #183, #231, #241, #252, #253, #257, #259, #267, #268]