readshapefile() raises incorrect error msg regarding shpproj and shapelib

还没有人认领这个 Issue。

When plotting a shapefile using readshapefile()

`m.readshapefile(shapefile_path, 'roads')`

I received this error message:

`ValueError: shapefile must have lat/lon vertices - it looks like this one has vertices
in map projection coordinates. You can convert the shapefile to geographic
coordinates using the shpproj utility from the shapelib tools
(http://shapelib.maptools.org/shapelib-tools.html)`

However, it appears that the specified module "shapelib" is no longer maintained or available. To add to the confusion, there is a completely different module that also goes by the name "shapelib" available on pypi and github, but that does not contain the functionality suggested above.

In regard to a suggested solution. I found the fix on this site to be useful for converting the shapefile and getting past this readshapefile() error.
http://fascicul.us/convert-display-shapefile-matplotlib.html

However, this conversion sometimes leads to a new error:

`ValueError: readshapefile can only handle 2D shape types`

Which I have yet to find a way to resolve

从 readshapefile() 入口点开始，检查建议使用 shapelib 中的 shpproj 的错误路径。重现所报告的转换以及随后出现的“only handle 2D shape types”失败，然后确定是指导还是处理方式不正确。完成标准是错误消息和转换指导准确反映可用工具及支持的 shape 类型。

由索引模型根据 Issue 内容生成。