frequency table in the chi square test doesn't respect the order of categories

[jbao]

e.g. when the counts of observed categories in both groups are as follows:

treat_counts
female     39364
male        6561
unknown     4474

control_counts
f               2
female     152099
m               2
male        24299
unknown     15084

the observed frequency table is:

observed_ct
female      male  unknown        f        m
0     0.0   39364.0      0.0   6561.0   4474.0
1     2.0  152099.0      2.0  24299.0  15084.0

[jbao]

This bug is related to pandas-dev/pandas#14600 and therefore won't be fixed here.