Patch for iostream support about rapidjson HOT 4 OPEN

I meant to flag this as an enhancement when creating the issue -- my 
apologies...

I had the same problem and fixed it this way. Also wrote an ostream wrapper.
One thing to mention about the istream wrapper:

int Peek() {
   return _is->eof() ? '\0' : _is->peek();
}

peek kind of has to check for eof, otherwise it will return -1 instead of '\0'

Is there a way to read the first of multiple top level objects - particularly 
when reading from stream/socket?