Support for GRDB 7

[groue]

This pull request addresses #72 by bumping the minimum GRDB version to 7.1.

@foxware00, @Lutzifer, I could merge right away, but maybe you'd prefer to giving this branch a test first.

Don't miss the Migrating From GRDB 6 to GRDB 7 guide.

[Lutzifer]

@groue Sorry, I'm quite busy with a project that does not use GRDB (yet), so I've not started upgrading any projects to GRDB 7 and therefore can't test.

[groue]

No problem, @Lutzifer! Thanks for replying. I hope the migration will be smooth when you start upgrading.

[foxware00]

Thanks @groue for the fast turn around. I'm just in the process of moving from cocoapods to spm so once that's complete i'll verify this for you and report back

[groue]

Thank you @foxware00. Don't rush: I'll probably merge anyway. We'll always be able to address your eventual feedback when it comes.

[tommyming]

I can also help on testing this if needed, just started migrating from cocapods to spm, and updating some packages.

[groue]

That would be nice @tommyming, thank you!

[tommyming]

@groue I have just add the package using DEV branch and done some basic compatibility test(e.g. database read/write using existing RxSwift Syntax), seems works fine with GRDB 7.

Please let me know if anything needs more testing, thanks!

[groue]

Thank you @tommyming for your help. I'll merge this PR very soon now!

[foxware00]

We're happy with this PR from our testing

[groue]

Thank you very much for your help! RxGRDB v4.0.0 has just shipped 🚀