twitter-server: Update documentation for Features
twitter-server: Update documentation for Features

Problem

The comment in the code/AdvancedServer.scala is phrased
a bit confusingly.

Solution

Re-write to hopefully be a bit more clear.

Result

Better documentation.

RB_ID=840281

BuoyantIO/twitter-server,BuoyantIO/twitter-server,twitter/twitter-server,BuoyantIO/twitter-server,BuoyantIO/twitter-server,twitter/twitter-server,twitter/twitter-server