Fixing closing tag error with small for Blaze compatibility

This corrects the following error:

```
While building package `billing`:
client/views/invoices/invoices.html:118: Expected "small" end tag
...d_end}}<small></span>           {{/if}}  ...
```

when using billing on Meteor 0.8.0.

It also fixes the `Handlebars` undefined issue in i18n that billing uses.