Fixed precompute issue (again) in ElasticNet and enet_path

The previous fix (https://github.com/scikit-learn/scikit-learn/commit/41ae851643625a2dc933fd0864a20bbd23a4e8cb) didn't change things (https://github.com/scikit-learn/scikit-learn/issues/1734) in the n_samples <= n_features case, as the value of precompute was unchanged and remained truthy.

Also, the same issue existed in enet_path, so I applied the same fix.
Fix setup.py to resolve numpy requirement
during pre-install. This should allow
'pip install numpy cython scipy scikit-learn'
to install scikit.

This fix is based of issue and fixes in Scipy:
https://github.com/scipy/scipy/pull/453
https://github.com/branden/scipy/commit/ad0dd3e883ca5b241dda6136eee921eb900077a0
ENH: add pre_dispatch option to cross_val_score
DOC Fix estimator unsupervised fit method signature

The previous version had repeated the same signature twice instead of describing the supervised and unsupervised cases.
maintenance scripts added for machine learning maps - needed for modifying the map in future
DOC rename lambda to alpha in plot_lasso_coordinate_descent_path. (Re)-Closes #903.
DOC clarification of parameter search
AdaBoost: use estimator weights in predict_proba
TST + DOC AdaBoostClassifier.predict_proba fix
COSMIT refactor AdaBoost code
DOC fetch_20newsgroups returns the text, not text files. see SO question: http://stackoverflow.com/questions/16615523/using-scikits-kmeans-to-cluster-ones-own-documents
DOC Fixed documentation of kernel parameters: sigm uses gamma, but not degree. Closes #1972.
ENH add multilabel support to PRF metric family

Support also in classification_report
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}
DOC rewrite descriptions of P/R/F averages and define support
DOC/COSMIT fix typos in What's New
DOC add some contributions to What's New