client -> google_client
Support Tumblr API

- $RUBOTY_TUMBLR_CLIENT=tumblr to use tumblr api always
- $RUBOTY_TUMBLR_CLIENT=hybrid to use tumblr api on unsafe requests (default)

Prior to use tumblr API, you have to set $RUBOTY_TUMBLR_API_KEY
Slack turns FQDNs to http URL
Merge pull request #1 from sorah/tumblr-api

Support Tumblr API