We don't need to require all of Fog using ~> 1.20

With the release of Fog v1.20.0, it is possible to only require the
specific parts of Fog that you need, e.g. `require "fog/aws/storage"`
which will load 36 classes, whereas `require "fog"` loads 698 classes
in my tests.
Refer to Fog in the global namespace
Merge pull request #1364 from bquorning/less-fog

We don't need to require all of Fog using ~> 1.20