Improve ndtypes documentation

[hameerabbasi]

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 (Add installation documentation #24)
  • Setup of development environment (Add instructions to set up the development environment. #25)
  • Use Cases (Document use-cases #26)
  • 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