wip
ENH prettier output from NMF example

Better stopword and noise filtering, increased n_samples to 2000
since the recent optimizations to tf-idf and NMF allow this.

Also some micro-optimizations to NMF itself.
[DOC] Typo fixes in documentation for Novelty and Outlier Detection
Merge pull request #2412 from rolisz/patch-2

[DOC] Typo fixes in documentation for Novelty and Outlier Detection
FIX failing test in NMF due to negative zeros
BUG: remove remaining utf-8 characters in docstrings.