Improve ND Types docs

[xmnlab]

Suggestions about http://ndtypes.readthedocs.io/en/latest:

• [ ] Improve the text on each section on the first page, adding the main idea of the project, propose and goals.
• [ ] Add a roadmap (?)
• [ ] Add a Getting Started section (see http://dask.pydata.org/en/latest/docs.html):
  • Installation
  • Setup
  • Use Cases
  • Examples
  • Community
  • Why libndtypes / Why ndtypes ?
  • etc
• [ ] Add a Development Guidelines section (see http://dask.pydata.org/en/latest/develop.html)
• [ ] Add a Funding section (see http://dask.pydata.org/en/latest/funding.html)

Some References:

• http://dask.pydata.org/en/latest/docs.html
• http://datashape.readthedocs.io

[xmnlab]

moved to xnd-all repo project