bundle update

Might as well do it now, before it's too late.

Importantly, it includes these fixes:
https://github.com/newrelic/rpm/blob/master/CHANGELOG#L239
https://github.com/puma/puma/pull/570

Which could potentially be some of the issues we've run into.

/cc @zendesk/samson @grosser 

### Risks
 - Some