Add ability to report t-statistics (similar to R's 'report' option)

[carterkd]

First, this repo is amazing and has been so incredibly helpful for me. Thank you!

Some academic fields (e.g. academic finance) usually have t-statistics below the estimates in tables (rather than standard errors or confidence intervals). R's stargazer allows this behavior with the 'report' argument. I'd love this option to be in place here.

[toobaz]

@carterkd sorry for the very slow reply. Could you check #88 ?