qcut bin formatting bugs
I'm reading CSV tables and then use qcut to bin the continuous numbers. Given the number of bins, most of the time the qcut works fine. However, some times, it doesn't function correctly. The following are some weird cases I got in the result levels index. Sorry I can't give the experimental data  now because I'm running it on a very large data collections and currently I'm not allowed to public the data

(1) When dealing with negative numbers, sometimes it gives [-117.-1,  1], This happens at the first bin index in my test case.
(2) when bin# is two, it gives results like [1, 2005], (2005, 2005]
(3)a bin result like this:  please note the value 0.993, and value 0.1
array([[0.6, 0.991], (0.991, 0.992], (0.992, 0.993], (0.993, 0.993],
       (0.993, 0.994], (0.994, 0.995], (0.995, 0.996], (0.996, 0.997],
       (0.997, 0.998], (0.998, 0.1], (0.1, 1.2], (1.2, 1.5], (1.5, 2.1],
       (2.1, 3.5], (3.5, 5.2], (5.2, 7.1], (7.1, 8.5], (8.5, 11],
       (11, 13.7], (13.7, 65.8]], dtype=object)

(2) and (3) might be caused by the same reason

I'm using pandas 0.8.1 thanks.
