move the get() and request() function to their own files

mostly so that it's easier to do the `dox --api` generation
lots of comments in preparation for dox API generation
README: generate the API section

Generated using:

  cat lib/client.js lib/request.js lib/get.js lib/reader.js lib/writer.js \
      lib/parse.js lib/stringify.js | dox --api >> README.md