Add context and doc op to complete middleware

I have modified Compliment and ac-cider-compliment to work exclusively over middleware (no direct calls) and removed map-literal code from the client. The suggested changes to cider-nrepl add support for passing context to Compliment, and add another operation for retrieving popup-docs.

After you accept this patch and maybe after running on snapshots for a while, I'll be ready to cut `0.1.0`.