ds.crosstab() doesn't show sig when sig_level<0.01

A bug in the crosstab method when styling the output that makes tests with alpha < 0.01 not show up in the results.

Example code:
```
sig_level=0.05/28
ds.crosstab('Q7','Region',sig_level=sig_level)
```
This would only give the cross-tabulation of counts and not the significant groups