Remove grammar from repo
git subrepo clone git@github.com:ingydotnet/chess-pgx.git ext/chess-pgx

{"local":
  {"subdir":  "ext/chess-pgx"
  ,"action":  "clone"}
,"remote":
  {"url":     "git@github.com:ingydotnet/chess-pgx.git"
  ,"branch":  "master"
  ,"commit":  "7f20d33"}
,"git-subrepo":
  {"version": "0.1.0"
  ,"commit":  "84dfbd6"
  ,"origin":  "git@github.com:ingydotnet/git-subrepo"}}
Grammer is now a subrepo: ext/chess-pgx
0.0.2