doc: add plots to docstrings and reference to in what's new
> Enhanced time series plotting; adaptation of scikits.timeseries matplotlib-based plotting code

Let's add sample plots to this.

Continuing discussion on doc, I suggest to take a similar approach like statsmodels:

http://statsmodels.sourceforge.net/devel/generated/statsmodels.graphics.functional.rainbowplot.html#statsmodels.graphics.functional.rainbowplot

The plot in the docs is generated from the docstring
the Sphinx source:
http://statsmodels.sourceforge.net/devel/_sources/generated/statsmodels.graphics.functional.rainbowplot.txt
the docstring:
https://github.com/statsmodels/statsmodels/blob/master/statsmodels/graphics/functional.py#L208
So  

```
.. ipython:: python

   ts = Series(randn(1000), index=date_range('1/1/2000', periods=1000))
   ts = ts.cumsum()

   @savefig series_plot_basic.png width=4.5in
   ts.plot()
```

could be moved to a docstrin in cases where it makes sense.

Can we not reuse the test code that may already be in the code base?
https://github.com/pydata/pandas/blob/master/pandas/tests/test_graphics.py#L39

The major problem is that the test writing set-up in pandas is highly modular while docstrings à la statsmodels are more verbose.

But, taking a second look at the docstring above, the tests could actually be used to produce doc plots:

instead 

```
.. plot:: plots/graphics_functional_rainbowplot.py
```

use

```
.. plot:: plots/file_with_plot_examples.py

```

In file  `file_with_plot_examples.py` you may for the mean time import the test functions.

On the other hand, such plot files:
https://github.com/statsmodels/statsmodels/blob/master/docs/source/plots/graphics_functional_rainbowplot.py
coudl be easily contributed by pandas users for more cases that core devs are probably thinging of currently.
