DOC: Link to Python standard encodings from read_csv documentation
Trying to make it easier to access the list of encodings from the documentation. Adding this was suggested on this [SO question](http://stackoverflow.com/questions/25530142/list-of-pandas-read-csv-encoding-list/25530279#25530279).

Thanks. Could you add it to the html documentation. That's under `doc/source/io.rst`.
I saw Jeff's comment on SO. I don't mind whether it's in the function docstring or not, but it would be a nice addition to the html docs.
 @dxshank can you only have 1 link (the python 3 is good). pls rebase and ping when green
 @jreback Sorry got sidetracked by some other stuff. Will rebase soon.
 @jreback @TomAugspurger : PR updated to link to only one list of encodings.
 ok, pls squash into a single commit and I think good 2 go
 @jreback : Changes squashed into a single commit
 gr8 thanks!
