First pass at re-worked stream features.

Stream features now use stanza objects!

Features are given a ranking that expresses the dependency
relationships (since only one feature is negotiated at a time, the
dependency graph can be replaced by a line).

>>> xmpp.register_feature('my_feature', _my_handler,
>>>                       restart=True,   # Requires stream restart
>>>                       order=600)      # Ranking (out of ~ 10,000,
>>>                                       # lower #'s executed first)

SASL mechanisms may now be added or disabled as needed. Each mechanism
is given a priority value indicating the order in which the client
wishes for mechanisms to be tried. Higher priority numbers are executed
first.

>>> xmpp.register_sasl_mechanism('SASL-MECH', _mech_handler,
>>>                              priority=0)

Disabling a SASL mechanism:

>>> xmpp.remove_sasl_mechanism('ANONYMOUS')

1 files changed, 52 insertions, 0 deletions

diff --git a/sleekxmpp/stanza/stream_features.py b/sleekxmpp/stanza/stream_features.py
new file mode 100644
index 00000000..5be2e55f
--- /dev/null
+++ b/sleekxmpp/stanza/stream_features.py
@@ -0,0 +1,52 @@
+"""
+    SleekXMPP: The Sleek XMPP Library
+    Copyright (C) 2010  Nathanael C. Fritz
+    This file is part of SleekXMPP.
+
+    See the file LICENSE for copying permission.
+"""
+
+from sleekxmpp.xmlstream import ElementBase, StanzaBase, ET
+from sleekxmpp.xmlstream import register_stanza_plugin
+
+
+class StreamFeatures(StanzaBase):
+
+    """
+    """
+
+    name = 'features'
+    namespace = 'http://etherx.jabber.org/streams'
+    interfaces = set(('features', 'required', 'optional'))
+    sub_interfaces = interfaces
+
+    def setup(self, xml):
+        StanzaBase.setup(self, xml)
+        self.values = self.values
+
+    def get_features(self):
+        """
+        """
+        return self.plugins
+
+    def set_features(self, value):
+        """
+        """
+        pass
+
+    def del_features(self):
+        """
+        """
+        pass
+
+    def get_required(self):
+        """
+        """
+        features = self['features']
+        return [f for n, f in features.items() if f['required']]
+
+    def get_optional(self):
+        """
+        """
+        features = self['features']
+        return [f for n, f in features.items() if not f['required']]