Support runner options for Docker Machine

See merge request !1

Update README.md

See merge request !3

CI: port Travis config to GitLab

See merge request !2

See #15

Fixed S3 secret key configuration

S3 access key was used as secret key

s3 support added

Add limit option for specific runner

Fix registration check when in Ansible check-mode

When running the playbook in `--check` mode, `gitlab-runner list` still needs to register a result to prevent an error on the following `when` clause.

Fix concurrency auto-detection

Auto-detect runner concurrency based on total CPU threads (vcpus), instead of only processor cores. This accounts for both multiple cores and multiple processors.

See https://stackoverflow.com/questions/39539559/ansible-procesor-count-vs-processor-cores-vs-processor-vcpus

Clean up scripts

package_name: make it possible to latest versions since gitlab 10.0

Docker privileged

debian: add possibility to fix package version number

no clue why i didn't get any email updates from github anymore..

fix: remove warning from Ansible 2.2

In order to fix the gitlab runner version