doc: lint README.md
doc: lint README.md

Fixes grammar, removes extra lines and spaces, etc. Also removes a few
references to `node-waf`, which was removed ~6 years ago now. Happy to
add back if people still need that information.

PR-URL: https://github.com/nodejs/node-gyp/pull/1498
Reviewed-By: Vse Mozhet Byt <39164014c1ea1d786372ed67424a3db1c9cda5d3@gmail.com>
Reviewed-By: Richard Lau <8193d74c06330af7778ef55510160e4e561ed6a1@uk.ibm.com>
nodegit/node-gyp,nodegit/node-gyp,nodegit/node-gyp,nodejs/node-gyp,nodejs/node-gyp,nodejs/node-gyp,nodejs/node-gyp,nodejs/node-gyp,nodegit/node-gyp,nodegit/node-gyp