Add numba for GPU examples

Author: gjbex

source-code/gpu/README.md

@@ -8,5 +8,7 @@ Sample code for performing computations on a GPU.
 1. `pycuda.ipynb`: jupyter notebook illustrating pyCUDA.
 1. `curand.ipynb`: jupyter notebook illustrating generating random
    numbers on a GPU.
-2. `scikit_cuda.ipynb`: jupyter notebook illustrating linear algebra
+1. `scikit_cuda.ipynb`: jupyter notebook illustrating linear algebra
    on a GPU device.
+1. `numba.ipynb`: jupyter notebook illustrating using numba for
+   GPU computing.