Rebase Docker image on the official Ruby 2.2 image.
Rebase Docker image on the official Ruby 2.2 image.

https://registry.hub.docker.com/_/ruby/

JetBrains/intellij-sdk-docs,develar/intellij-sdk-docs,JetBrains/intellij-sdk-docs,develar/intellij-sdk-docs,artspb/intellij-sdk-docs,develar/intellij-sdk-docs,artspb/intellij-sdk-docs,breandan/intellij-sdk-docs,artspb/intellij-sdk-docs,chashnikov/intellij-sdk-docs,chashnikov/intellij-sdk-docs,breandan/intellij-sdk-docs,JetBrains/intellij-sdk-docs,chashnikov/intellij-sdk-docs,chashnikov/intellij-sdk-docs,breandan/intellij-sdk-docs,artspb/intellij-sdk-docs