Upgrade to 1.7.17

![getinsertpic.com](http://media3.giphy.com/media/kR8Qr8NvYu3bq/200.gif)
*^ pimp my ride*

> Note: `JRUBY_VERSION` is defined as a BUILD PARAM in the CI job for this repo 
(https://jenkins.news.cloud.bbc.co.uk/job/jruby-rpm/)