Add Update and delete support

[michaelmior]

No description provided.

[DrOvonN]

I tried your gem with some SQL-queries and had some problems with the identifiers for example.
UPDATE users SET id=1 WHERE id=0 -> parse error on value "UPDATE" (identifier)
DELETE FROM users WHERE id=1 -> parse error on value "DELETE" (identifier)

[michaelmior]

Updates are not currently supported. That's what I was attempting to add with this PR.