RF: reduce boiler-plate.
ENH: Implementation of the Westin tensor stats.
PEP8
RF: Change the name to imply that this actually does something with the input.

Rather than just 'checking' it. Also, changed the order of operations to
'short-circuit' the shape-checking.
DOC: Reformat the citation.
Merge pull request #170 from arokem/westin_stats

Westin stats