Failing at differently sized groups

Thank you for a great library. There seem to be a bug for some numbers patterns with Indian style grouping (the default in Indian English, for instance):

```
> format("#,##,##0.###",2000000)
'2,000,000'
```
(Excepted: `20,00,000`)

For reference, here's how it looks in Google Closure: https://github.com/google/closure-library/blob/master/closure/goog/i18n/numberformat.js#L892