GetStructuringElement returns a kernel that can be used to perform
morphological operation. This function can be available in `cv.imgproc`
and takes two arguments, the erosion type (MORPH_RECT, MORPH_CROSS,
MORPH_ELLIPSE, ...) and the size of the generated kernel. The `ksize`
argument must be an array of two numbers.
The output kernel is often use for Dilation and Erosion operations.
Now building and passing tests locally in node v0.10.40 v0.12.7 and
v4.1.1. Other modules would not build at node lower than v0.10, so I
stopped there.
