[gem] minor gem updates.
[gem] minor gem updates.

`gem update --system`
`gem update bundler`
`bundle update`

* gem version: 2.4.8
* bundler version: 1.10.5

Note: the “reek” code analysis tool is still not working. 
grantneufeld/Wayground,grantneufeld/Wayground,grantneufeld/Wayground,grantneufeld/Wayground