ContentSniffer.sniff

string sniff(soup.message.Message msg, glib.bytes.Bytes buffer, out string[string] params)

Sniffs buffer to determine its Content-Type.

The result may also be influenced by the Content-Type declared in msg's response headers.

`msg`	the message to sniff
`buffer`	a buffer containing the start of msg's response body
`params`	return location for Content-Type parameters (eg, "charset"), or null

the sniffed Content-Type of buffer; this will never be null,

but may be application/octet-stream.