Release 1.8.0

Changelog

• Changed: Updated default docker-machine version to 0.16.0
• Changed: Updated default gitlab runner to 11.6.0
• Added: Configuration parameters for post_build_script, pre_clone_script, request_concurrency and output_limit. #22
• Added: Configurable docker image for runner #27
• Added: Add pre/post install user-data snippets for runners #26

Contributions

• Configurable docker image for runner #27 by mkalmykov
• Add pre/post install user-data snippets for runners #26 by rsrchboy
• Add cache_bucket_prefix, to allow for unique bucket names #25 by rsrchboy
• Rename CHNAGELOG.md to CHANGELOG.md #24