doc: link dialeg definition to python docs

[timmie]

http://pandas.pydata.org/pandas-docs/stable/io.html#io-dialect

to

http://docs.python.org/library/csv.html#csv.Dialect

using intersphinx

[timmie]

please add tags: community, doc

[wesm]

Could you lend a helping hand?

[timmie]

sure.
But I am quite busy till mid end of this week...