Switch from TSD to Typings

TSD is deprecated and causes GH 403 errors, so we will be switching to Typings.

For more information, see the GH issue that msavy_jira opened up in the Typings repository: https://github.com/typings/typings/issues/128

Typings: https://github.com/typings/typings
TSD: https://github.com/DefinitelyTyped/tsd