More Yesod benchmark stuff

I've been in benchmarking mode since yesterday, working on both this set and the TechEmpower benchmarks. The benchmarks you have here were a great way to motivate simple tweaks to get better results in the TechEmpower benchmarks, which should result in a much better showing for Haskell next time around, so thank you again!

Anyway, here are some more tweaks. You may be interested in looking at the third one more closely, it *should* be a simple tweak that can be applied to the other three as well to increase their performance.