Add support for Statistics endpoint.

[tmcgilchrist]

See https://github.com/mirage/ocaml-github/issues/86 and https://developer.github.com/v3/repos/statistics/.

[Aaylor]

I have an issue while testing the weekly commit count API function: an error occurs during the parsing:

Testing weekly commit count.
Fatal error: exception (Failure
   "Bad response: Yojson.Json_error(\"Line 1, bytes 0-33:\\nExpected '{' but found '[[1329609600,5896,-6],[1330214400'\")\
  \nJSON body:\
  \n[\
  \n  [ 1329609600, 5896, -6 ],\
  \n  [ 1330214400, 1848, -1339 ],\
  \n  [ 1330819200, 0, 0 ],\
  [....]
  \n  [ 1598140800, 0, 0 ],\
  \n  [ 1598745600, 39, -5 ],\
  \n  [ 1599350400, 0, 0 ]\
  \n]")

Here is the snippet I used to test the function:

let test_weekly_commit_count =
  let token = ... in
  let user = "mirage" in
  let repo = "ocaml-github" in
  let open Github in
  Format.printf "Testing weekly commit count.@.";
  let weekly_count =
    let t =
      let open Monad in
      run (Stats.weekly_commit_count ~token ~user ~repo () >|= Response.value)
    in
    Lwt_main.run t
  in
  let pp_sep fmt () = Format.fprintf fmt "; " in
  Format.printf " all: [ %a ]@."
    (Format.pp_print_list ~pp_sep Format.pp_print_int)
    weekly_count.Github_t.participation_all;
  Format.printf " owner: [ %a ]@."
    (Format.pp_print_list ~pp_sep Format.pp_print_int)
    weekly_count.Github_t.participation_owner

[tmcgilchrist]

I've added a rudimentary executable that pokes at mirage/ocaml-github and dumps a partially formatted representation to stdout. Is there anything else you'd like to see added @Aaylor @avsm ?

[Aaylor]

Thanks, it looks good to me; I've run succesfully the different endpoints.