code: public static boolean save(String tableName, String primaryKey, Record record) {
  		return MAIN.save(tableName, primaryKey, record);
  	}
docs: Save record.
  <pre>
  Example:
  Record userRole = new Record().set("user_id", 123).set("role_id", 456);
  Db.save("user_role", "user_id, role_id", userRole);
  </pre>
  @param tableName the table name of the table
  @param primaryKey the primary key of the table, composite primary key is separated by comma character: ","
  @param record the record will be saved
  @param true if save succeed otherwise false