make it possible to use any namespace with the ConditionNode
use deferreds for the connection
allow to inherit from client
initial roster support
use clean_ validators even when value is undefined and not required
updated roster signal implemented
BOSH fixes:
    1. start new blank query immediatly even if we don't have anything
    to send
    2. dispatching of stanza leads to change of parent, so always use
    the first one
use polling value only if the session is polling
some notes
dispatcher: fix a situation when handler returns null, typos
use undefined value to indicate that StringNode is absent, null to
indicate that it's a self-closed tag
initial vcard support
remove extra commas
DateTime fields and types are added
XEP-0203 support added