Convert expected arguments to driver values

[Gediminas Morkevicius]

Currently if expected argument is not converted to a supported driver.Value. That means the matching might be not exact or in some cases misleading and requires an user to expect already converted arguments.
Sqlmock should perform the same conversions as sql library for all expected arguments. That will be backward compatible and acting more as expected.

The changes may affect time.Time comparison, since it will be more strict.
The good outcome is that an error message for argument comparison will be more precise and will show exactly which argument did not match.