Add module swf.models.history.builder with the History class

This class allows to build a dict that represents a history such as what
SWF passes to a decider.

Author: ggreg

setup.py

@@ -37,10 +37,11 @@
     packages=[
         'swf',
         'swf.actors',
-        'swf.models',
         'swf.querysets',
 
+        'swf.models',
         'swf.models.event',
         'swf.models.decision',
+        'swf.models.history',
     ],
 )

swf/models/history/__init__.py

@@ -0,0 +1 @@
+from base import History