Writes the migration of the table where Masu.History.Ecto keeps the
history of grids' cells, for the repo that keeps it (the app's own, or
another: --migrations-path priv/history_repo/migrations).
$ mix masu.gen.history
$ mix masu.gen.history --table grid_history --migrations-path priv/other_repo/migrations
Then run mix ecto.migrate.
Options
--table- the table's name,masu_historyunless given (pass the sametabletouse Masu.History.Ecto).--migrations-path- where to write it,priv/repo/migrationsunless given.