Merge pull request prometheus#39 from promlabs/release/v0.20.0

cut 0.20.0

Merge pull request prometheus#37 from promlabs/release/v0.19.0

cut 0.19.0

Merge pull request prometheus#32 from promlabs/release/0.18.0

cut 0.18.0

Merge pull request prometheus#30 from promlabs/release/0.17.0

cut 0.17.0

update release date in changelog

Signed-off-by: Augustin Husson <husson.augustin@gmail.com>

release v0.15.0

release v0.14.0

release v0.13.0

release v0.12.0

release v0.11.1