Flux: The Julia Machine Learning Library
Flux is a library for machine learning. It comes "batteries-included" with many useful tools built in, but also lets you use the full power of the Julia language where you need it. The whole stack is implemented in clean Julia code (right down to the GPU kernels) and any part can be tweaked to your liking.
Install Julia 0.6.0 or later, if you haven't already.
Pkg.add("Flux") # Optional but recommended Pkg.update() # Keep your packages up to date Pkg.test("Flux") # Check things installed correctly
Start with the basics. The model zoo is also a good starting point for many common kinds of models.
See GPU support for more details on installing and using Flux with GPUs.