Update Rubocop version to 0.25.0

Ensure we're linting our code with the latest version.

Change-Id: I5f160bf55ebb574846f77b251460abe5e6a7b18c
Reviewed-on: http://gerrit.causes.com/41744
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>