ENH: PySide support for qtpandas.
Added PySide support for the qtpandas DataFrameWidget.

Please add a note to doc/source/release.rst (which you can just squash into one commit) and it'd be great if you could change the name of the commit to `ENH: Add PySide support for qtpandas.` 
 I would move this out of sandbox maybe to pandas.utils?
 @jreback In my opinion it's still just an example... Lacks a lot of features to be a full DataFrame widget... (adding/deleting rows and columns, better type support, better edit, etc...)
 oooh haha didn't realize this was sandbox. Your call if you want to put in release notes.
 @jreback Done.
 Can we stick a little doc section somewhere that describes this ? Maybe visualiztion? @cpcloud  where do you think
 `visualization.rst` is fine
 Should I open a new issue? "DOC: Add docs for qtpandas"?
I don't know what should I write there? :) This was just a support thing for PySide. :)

Maybe I can write a paragraph like: If you want to visualise your DataFrame in a Qt application you can use the DataFrameWidget like this: ... example ... And thats it :) But I would need to create a new section: Visualizing data in Qt... Or something like that...
 @alefnula up to you whether u want to create a new issue. what you just suggested sounds fine
 @alefnula just create a small section in visualization, you can include in this PR
 Added.
 @cpcloud @jtratner  ?

ok with me
 looks like it needs one more rebase then good 2 go
 @alefnula thank you
