Cannot specific minor versions

[paulo-ferraz-oliveira]

At the moment, because we support version ranges, stuff like 23, or 22.3 might get converted to a later version.
While this is surely useful to some it's also confusing to others (me included). We should add (by default, for backward compatibility it should be loose) a version option with both strict (use what the user wrote) or loose (try to guess stuff). This would also probably solve #46.