Added EDN to Benchmark and refactored server to DRY it a bit

Hello, @swannodette !

I am excited to make my first pull request to your repo!
But I am not sure if my changes fits the main goal of your project to show how to use Transit.
It definitely added unnecessary complexity by adding obsolete EDN implementation to benchmark.

Please, think twice before approving my pull request:)
I will not mind if you reject it and benchmark with EDN will be only in my fork.

Thank you for this simple example of using Transit and for all of your awesome work!
Transit Rocks!