hadley/httr — pull request #36 by jdeboer (2013-05-14 11:20:46+00:00)
Title: Added functionality to refresh expired OAuth2.0 access tokens

Added:
1. a use_by date-time field to OAuth2.0 access tokens.
2. a function to check whether a token's use_by date-time has passed (expired) within a specified number of seconds (margin)
3. a function to refresh an OAuth 2.0 access token