More time.Time format scanning support

#35 (closed) improved time.Time scanning but only for the format used by time.Time.String. There's a TODO for supporting formats similar to mattn/go-sqlite3 in a backwards-compatible way.

The reddit thread announcing v1.9.0 had a comment mentioning this was a problem.

There was discussion in Gophers #sqlite about what mattn/go-sqlite3 does and how this package might support more formats. Before that, there was discussion in #performance about formats listed at https://sqlite.org/lang_datefunc.html and how to support them.