Mock Time

[tooolbox]

Closes #8

Adds the ability to mock time for the purpose of unit tests. Uses the IFNULL(?, UTC_TIMESTAMP()) strategy described in #8.

Depends upon #10 because it will be annoying to unit-test this without a proper Go client 😉

[tooolbox]

I realized that this did not actually depend upon #10 because all the changes were taking place in the table package and that could be unit-tested without the Client, which is why you don't see that in this PR.

Still, between this and the Client, it will be smooth to unit-test the upcoming ISO8601 support.

Sorry for all the branch merging, I'm maintaining a few here trying to keep different features separate and I got confused 😉

The table package could be unit-tested more thoroughly but for now it has a basic test and you can see how the time-mocking comes into play. I do still need to figure out how I'm going to expose the time-control to outside packages (both inside and outside of this repo) but I don't think it will be difficult.

I'm pleased that this solution allows for mocking the time while preserving the DB as the single time source. The only snag I ran into is that the Mysql driver doesn't support multiple statements in a single Exec—if they contain placeholders—so I had to touch the UpdateInstance call more than I wanted to, but I think it turned out fine.