DOC: date_range method instead of DateRange
In the the beginner [tutorial](http://pandas.pydata.org/pandas-docs/stable/10min.html#object-creation), the DataFrame example uses `pd.data_range` where `pd.DataRange` is the correct method.

As a beginner, I'm not sure if the documentation is old or my version of pandas is. Also, I don't know how to tag this issue as "Docs"
