Update coordinate_descent.py

Reverting _dense_fit to explicitly check precompute == True rather than just looking at its truthiness.

Should prevent unwanted precomputing, see https://github.com/scikit-learn/scikit-learn/issues/1734
Merge pull request #1736 from jamestwebber/patch-1

Update coordinate_descent.py
ENH set min_df in fe.text back to 1

2 is simply too confusing for users, since it causes trivial examples
to fail.
DOC improve mini-batch k-means narrative
COSMIT Moved the test_roc_curve_one_label test where other ROC curve tests are.
Merge pull request #1740 from tjanez/move_roc_curve_test

COSMIT Moved the test_roc_curve_one_label test where other ROC curve tests are
COSMIT pep8
FIX for iid weighting in grid-search
DOC FIX finite precision