[TASK] Update the CI-related gems.

This change also adds a RuboCop configuration to disable line-length
checks for HAML files which have been introduced in a recent version
of haml-lint.

Also change concatenations using "+" in void context in HAML files to
use the "succeed" Haml helper.

Resolves: GET-11
Merge pull request #54 from braingourmets/task/update-ci

[TASK] Update the CI-related gems.