added qtoml to benchmark

[marzer]

  pytomlpp:   0.6545989999999993 s
      toml:   4.953170199999999 s
     qtoml:   7.352302399999999 s
   tomlkit:  31.071474500000004 s

^_^

I also re-added toml++ submodule with correct https URI, because the previous non-https URI would cause clone failures for some remotes (more info here: https://stackoverflow.com/questions/13509293/git-fatal-could-not-read-from-remote-repository)

[bobfang1992]

LGTM!