Add lister reference

docs/source/configuration.rst

@@ -133,4 +133,5 @@ References
 
    configuration/reference
    configuration/segments
+   configuration/listers
    configuration/local

docs/source/configuration/listers.rst

@@ -0,0 +1,21 @@
+****************
+Lister reference
+****************
+
+Listers are special segment collections which allow to show some list of 
+segments for each entity in the list of entities (multiply their segments list 
+by a list of entities). E.g. ``powerline.listers.vim.tablister`` presented with 
+``powerline.segments.vim.tabnr`` and ``….file_name`` as segments will emit 
+segments with buffer names and tabpage numbers for each tabpage shown by vim.
+
+Listers appear in configuration as irregular segments having ``segment_list`` as 
+their type and ``segments`` key with a list of segments (a bit more details in 
+:ref:`Themes section of configuration reference <config-themes-segments>`).
+
+Currently only Vim listers are available.
+
+Vim listers
+-----------
+
+.. automodule:: powerline.listers.vim
+   :members:

docs/source/develop/segments.rst

@@ -1,3 +1,5 @@
+.. _dev-segments:
+
 ****************
 Writing segments
 ****************