Postgres version invalid regex

[sderosiaux]

Hi,

In is_pg_at_least_nine_two the regex expects three parts "x.y.z" but some PostgreSQL version only has 2 parts, ie: "12.3" (since 11 it seems https://www.postgresql.org/support/versioning/) hence most commands fails with 'NoneType' object has no attribute 'groups'.

[samkit-jain]

I too encountered the same. Have fixed in #7