Model#destroy & Model#update

[7imon7ays]

Should be able to call model.update({ foo: "bar", baz: null }) and model.destroy(). Both require models to track what row they're in.

To reproduce the behavior of a regular spreadsheet, Model#destroy should remove the entire row. This has the side-effect of changing the row number of every record with a greater row number.

Possible solutions:

1. Mark deleted record's row as "archived" instead of removing it. Bad: Sheet eventually becomes filled with junk**. Poor usability and performance.
2. Require a separate, unique, non-null column in every sheet to identify records after rows have been deleted. Bad: Too big a requirement from the user.
3. Keep every instantiated record in an array, sorted by row number. When a record is deleted, update the row number of all instantiated records that had a greater row number. Bad: Deletion becomes Log(n) + n / 2 operation. Log(n) at worst to find the first instance with a greater row number in the sorted array + n/2 on average to update those rows. Race condition if the user manually changes the sheet while Goodel is running.

Option 3 looks best.

** Not a bad idea to have an "archive" instance method. Opened #8.