BUG: Series.__iter__ not dealing with category type well (GH7839)
Merge pull request #7842 from jreback/cat_iter

BUG: Series.__iter__ not dealing with category type well (GH7839)
DOC: add link to SettingWithCopy warning/error message (GH7658)
COMPAT: SettingWithCopy will now warn when slices which can generate views
        are then set