GeoJSON 1.0a4

GeoJSON, the Python project, is a reference implementation of GeoJSON, the format specification, and also of the Python geo interface. Matthew Russell and I have brought it up to date with the current draft version of the spec and uploaded 1.0a4 to PyPI.

Before the final 1.0, I think we need to rename this. The package name, "geojson", is fine, but a new project name would invite less confusion with the specification project.