Consume RubyGems updates from api/v1/timeframe_versions.json endpoint instead of api/v1/activity.

[calebbrown]

RubyGems has a stable API for consuming versions changes that can be paginated across all the results in a 7 day timeframe.

This should be more reliable than RSS for retrieving new package versions.

See: https://guides.rubygems.org/rubygems-org-api/#get---apiv1timeframe_versionsjson

$ curl 'https://rubygems.org/api/v1/timeframe_versions.json?from=2019-01-18T21:24:29Z&to=2019-01-18T21:24:31Z

/api/v1/activity/latest is limited to the last 50 results.