v0.22.6

Improvements for integers (#120)

Integer constants are now always parsed as BIGINT and integer types
(`SMALLINT`, `INTEGER` and `BIGINT`) are stored as an i64 in the Value
rather than storing them in the existing f64 which will lose precision
of the integer.

This allows use to raise a new SQLSTATE 22003 "numeric value out of
range" in most cases. However, this is not entirely complete as the
minimum value for BIGINT cannot be encoded corrected. See #116.