New readme

[hakunanatasha]

Updated readme to reflect lightwood.

Make sure the new docs are also updated to reflect to the docs link : )

[paxcema]

There's bits of the README already in the contributing guide. Apart from that (and a small note), looks OK

[hakunanatasha]

Adds the updated index.rst doc file and README to the autobuild docs; the autobuild is needed in order to have the up-to-date documentation links properly pointing in the right direction.