Added shields badge to widgets page

Mentioned in #1145. 

This should change the i18n files but the last update was in march so I'm guessing we aren't updating the translation files every time a change is made? @Changaco 

The badge currently displays $NaN/week for anonymous givers, I'll send [shields](https://github.com/badges/shields) a PR for that. 

EDIT: badges/shields#277 merged in.