Feature/rom update messages upsert

[joelvh]

This adds overwrite capability to the ROM adapter. Supercedes #463 to use UPSERT instead of batch UPDATE statements.

[joelvh]

@paneq @pawelpacana how do we specify to install Sqlite 3.24+ on TravisCI for upsert capability?

[joelvh]

@paneq @pawelpacana saw that you're skipping tests for sqlite. Got things working and merging to master.

[mostlyobvious]

saw that you're skipping tests for sqlite. Got things working and merging to master

I'm glad it worked! There's an open issue to support sqlite (#446) which is why test might have been skipped.

We've moved most of the tests to CircleCI (some still left on TravisCI) and those run on docker images based on CircleCI ones. They have sqlite in version 3.16.2-5+deb9u1. If you know how to add sqlite 3.26 to Debian Stretch I could push new images.

[joelvh]

@pawelpacana Looks like they released support in v0.26.0 of AR Import (based on the comment on zdennis/activerecord-import#540 (comment)

I opted to detect whether Sqlite 3.24.0+ is being used, otherwise throw an exception when using the overwrite feature.