Refactor charts resource. Improved charts code

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Show commit sha for build duration. Fixed tests

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Use minutes for duration chart

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Fix Charts::BuildTime spec

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add entries to CHANGELOG

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>
Add CONTRIBUTING.md

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>