DOC: add concat to top-level API table

Author: tacaswell

doc/source/index.rst

@@ -25,12 +25,13 @@ github https://github.com/matplotlib/cycler
 
    cycler
    Cycler
+   concat
 
-
-The public API of :py:mod:`cycler` consists of a class `Cycler` and a
-factory function :func:`cycler`.  The function provides a simple interface for
-creating 'base' `Cycler` objects while the class takes care of the composition
-and iteration logic.
+The public API of :py:mod:`cycler` consists of a class `Cycler`, a
+factory function :func:`cycler`, and a concatenation function
+:func:`concat`.  The factory function provides a simple interface for
+creating 'base' `Cycler` objects while the class takes care of the
+composition and iteration logic.
 
 
 `Cycler` Usage