fractal contour length

[miniufo]

It is interesting to integrate a function that calculates the length of tracer contour and the fractal dimension of it.

• The length of a contour can be calculated using find_contours method in the skimage.measure package, which adopts a marching-cubes algorithm;
• The fractal dimension can be calculated using box-counting algorithm.

This two methods will certainly enrich the xcontour package. Also, the returned results could be a function of equivalent latitudes.

[miniufo]

This is almost done. And the paper (in Chinese) is ready to be accetped. There will be a commit recently and a update on the README.md.