DOC fix typos
COSMIT shorten long line for pep8
ignore PDFs
ENH Create FeatureSelectionMixin for shared [inverse_]transform code

Also rename FeatureSelectionMixin -> SelectorMixin -> _LearntSelectorMixin
And rename sklearn.feature_selection.{selector_mixin -> from_model}
ENH Create FeatureSelectionMixin for shared [inverse_]transform code

Also rename FeatureSelectionMixin -> SelectorMixin -> _LearntSelectorMixin
And rename sklearn.feature_selection.{selector_mixin -> from_model}