matplotlib/matplotlib — pull request #3018 by captainwhippet (2014-04-28 08:13:19+00:00)
Title: Fix documentation of entropy function

Fix the documentation of the entropy function to correct the formula so
it reflects the calculation used in the code. Also mention the unit of
the value returned,

See also this stackoverflow question: [Matplotlib mlab entropy calculation incorrect?](http://stackoverflow.com/questions/23291576/matplotlib-mlab-entropy-calculation-incorrect)