Add STRICT flag to createtable!

[torrance]

Recent versions of SQLite have the option to set a table to STRICT, which makes SQLite:

• require each column of the table have an explicit type
• enforce types, rather than accepting any type during row insertion/updates

Currently createtable!() does not include the option to set STRICT as true. This issue is a feature request to add this as a boolean flag to this method.

[quinnj]

Sounds like a great idea; feel free to open a PR if you're up for it!