Refactoring, small improvements, and cleaning notation of IsotonicRegression
Changing docs from "vector" to "1d array"
Reverting array X to vector x rename
Docstring addition and x->X
Incorporating @ogrisel's comments for simplification
More simplifications
Fixing simplification for clip
Adding test coverage for weight deprecation in IsotonicRegression and isotonic_regression
DOC add Data Publica testimonial
Improving exception and warning coverage
Merge pull request #3250 from mjbommar/isotonic-refactor-2

[MRG+1] Refactor and clean IsotonicRegression
WIP: releasing the GIL in the inner loop of coordinate descent
Replaced numpy calls with blas in dual_gap
Made the following fixes
1. Replaced l1_norm with dasum calls
2. Changed strides to n_tasks in ddot
Replaced multiprocessing with threading
ENH: Release the GIL for sparse coordinate descent
COSMIT: Replaced xrange with range
ENH: Release GIL in the gram variant
Replaced C ordered contiguity and added typed memory views
Added typed memory-views for H and XtA