Added Attract extension.

For now it just contains a management command, but I ensured it is
registered properly through the Pillar extension system.

bcloud/attract/extension.py

@@ -0,0 +1,43 @@
+"""Pillar extension for Attract."""
+
+from pillar.extension import PillarExtension
+
+
+class AttractExtension(PillarExtension):
+    @property
+    def name(self):
+        return u'Attract'
+
+    def flask_config(self):
+        """Returns extension-specific defaults for the Flask configuration.
+
+        Use this to set sensible default values for configuration settings
+        introduced by the extension.
+
+        :rtype: dict
+        """
+
+        # Just so that it registers the management commands.
+        from . import cli
+
+        return {}
+
+    def blueprints(self):
+        """Returns the list of top-level blueprints for the extension.
+
+        These blueprints will be mounted at the url prefix given to
+        app.load_extension().
+
+        :rtype: list of flask.Blueprint objects.
+        """
+        return []
+
+    def eve_settings(self):
+        """Returns extensions to the Eve settings.
+
+        Currently only the DOMAIN key is used to insert new resources into
+        Eve's configuration.
+
+        :rtype: dict
+        """
+        return {}