Pandas apply a func into a whole dataframe : I have a data frame, I want to apply `func=lambda x: max(x)-min(x)`
into the table below.

                a       	b       	c
    Utah 	0.907184 	0.000049 	0.550308
    NY 	    0.129423 	1.606726 	2.041340
    DC 	    0.228202 	1.041567 	0.007727
    Texas 	0.947254 	0.000211 	0.346336
if I do `df.apply(func)` it'll return, calcuated in the axis:

`a   -0.613516
 b   -1.260598
 c   -1.340853
dtype: float64 `

I want to take the max of all 12 data, and minus min of all 12 data,
return a dataframe of 4x3.