[Feature Request] Add concise xlabel=, ylabel=, option in plot() method
The current [plot()](http://pandas.pydata.org/pandas-docs/version/0.15.1/generated/pandas.DataFrame.plot.html#pandas.DataFrame.plot) method for Dataframe cannot set the x/y label in it. [Result](http://stackoverflow.com/questions/21487329/add-x-and-y-labels-to-a-pandas-plot?lq=1) is more lines of code for just doing this. 

As someone commented in that post:

> Is there a particular reason why x and y labels can't be added as arguments to pd.plot()? Given the additional concision of pd.plot() over plt.plot() it seems it would make sense to make it even more succinct instead of having to call ax.set_ylabel()
