Upgrade Rubocop for Travis builds from 0.25.0 -> 0.26.0

In the process, we've also decided to switch access modifiers from
outdented style to indented, keeping us in line with the defaults.

Change-Id: Id578bffad07009a8b5c9e1fe9c9a3858f8e57ccd
Reviewed-on: http://gerrit.causes.com/42250
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>