Support for PostgreSQL

I see that some SQL queries and migration are designed primary for MySQL and won't be able on PostgreSQL out-of-the-box.

Do you guys interested in supporting postgres? Will you accept PR?

Start by auditing the SQL queries and migrations described in the issue, comparing their MySQL assumptions with PostgreSQL behavior. Done means the library supports PostgreSQL out of the box and the relevant migrations and queries work there; no files or tests are named, so repository-wide investigation is required.

Written by the indexing model from the issue text.