Change Timecop to use blocks (easy changes)

It is best to avoid `Timecop.travel` with `Timecop.return`. Instead, the prefered syntax is to use `Timecop.travel` with a block.

I've had to track down a number of tests where there is a `travel`/`freeze` but no `return`. Very hard to find and sporadic.

This PR converts the `travel` to use the safer block format for some easy cases.
At some future date I may dive into converting all the more difficult ones and successfully convert out app to `Timecop.safe` mode.