BUG: Fix boxplots with manual numpy array of confidence intervals

Basically, I had some of the user input validation logic incorrect for numpy arrays of confidence intervals on the boxplots. This is a very minor fix, with a test and baseline image. 

Hopefully this can sneak in before 1.3.1.

Looking down the road a bit, I would like to propose splitting up `axes.boxplot` into two method:
 + one for the user to feed in some data, and get a graphs
 + a second to draw a single boxplot  onto an `axes object.

The idea here is that the first, high-level method calls the second. The second method allows users to place the elements of the boxplot where ever they want. But that's neither here nor there.