v0.0.3

Additions:

* Add more context to error messages.

Fixes:

* Mirroring and fetching from 'git://' URLs caused timeout errors.
  Switch to 'https://' URLs.
* Existing mirrored repositories with new commits were not updated.
  Previously, only the GitHub repository's `updated_at` field was used
  to determine if new changes were available. New pushes to a
  repository, however, don't change the `updated_at` field, but the
  `pushed_at` field.  Now both date-times are used when checking for
  updates.