Support objection v2

[devinivy]

As far as I can tell this already works great with objection v2, and it just needs to declare that as a peer dependency. It's worth noting that db-errors is now used directly by objection, so issues could arise in the future if this module's db-errors dependency isn't identical to objection's. With a breaking change this library could probably drop support for objection v1, remove the wrapError() call, and be less likely to get into dependency tangles.

[coveralls]

Pull Request Test Coverage Report for Build 15

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 14:	0.0%
Covered Lines:	213
Relevant Lines:	213

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💛 - Coveralls

[optii]

Looks good to me, haven't had time to dig into the objection v2 changes, but I did notice that the DbErrors had been integrated, and making the changes you suggest above seem like the right way forward. I will open an issue to re-state what you said above, as to not loose it.