Allow Query() to accept parameterized SQL values

[zacharyvoase]

This way we can benefit from Go's built-in SQL escaping routines without having to do DB-specific string escaping in the load testing script itself.

[imiric]

Hey, thanks for this!

LGTM, but could you add a usage example of it in the tests/ directory? Just for SQLite would be fine.

I'd like to eventually turn these into proper tests and hook up CI here, but well, priorities :)

[zacharyvoase]

Done, I added it for all three examples (I'm currently using it successfully with postgres, actually).

[zacharyvoase]

Thank you so much!