Dynamic shape files

[andybeet]

Add text in the README indicating that some shape files change frequently over time

What exactly do we mean by dynamic shape files? That the shape files are continuously changing (like wind areas because they are under development) or that depending on the season the area shifts? like a closure?

If the latter, not sure i would see that as a problem.
If the former, may be best to not include these yet unless there is a burning need
@jmhatch