Use "tegola style" for tests

[mpgerlek]

(from @ARolek)

https://github.com/go-spatial/tegola/blob/master/cache/redis/redis_test.go#L212

• this allows us to run tests in parallel which is nice for situations when tests are written that accidentally rely on previous tests (i.e. setting a package var)
• also the test logs output the names (i.e. "over_max_zoom" would show up in the logs)
• we're migrating the code base to this structure and it's all supported as of Go 1.7