Fix Viadeo module interpretation errors (#366) and Weibo authentication

This pull requests fixes the Viadeo module, replacing the use of the `restler` package with that of the `request` package, which is already a dependency of `everyauth`. Originally reported in issue #366.

Additionally, this pull request fixes an error in the Weibo module which will cause any other authentication modules to fail validation. The cause is in the Weibo module's modification of the `fetchOAuthUser` step, which is added to the error reporting sequence `authCallbackErrorSteps` instead of `callbackPath`.