Updated `sx-request-make` to use a consistent format for both `POST` and `GET` methods

  (sx-request-make): Added optional arguments for using "POST" and AUTH
  when performing requests
  (sx-request--build-keyword-arguments): Add option of using AUTH and
  including in query when required.
  (sx-request-build): Removed
  (sx-request--request): New function to perform query with all
  variables let bound.

  sx-auth.el: Updated `sx-auth-root` to be full auth URL rather than
  lack method.
  (sx-auth-authenticate): Remove dependency on `sx-request-build` and
  perform construction inline.
Sounds good to me.