Poor man stream parsing

I have two processes that communicate to each other via stdin and stdout/stderr. I wanted to use edn, but couldn't use regular `EDN::Reader` because when i'm reading from stdin, i read in chunks. `EDN::StreamReader` adds this ability.

It's not the best implementation in terms of speed (it attempts to parse the buffer every time there is a new chunk), but it does the job and is very simple.