Merge pull request prometheus#1914 from prometheus/beorn7/release

Cut v1.0.2

Merge pull request prometheus#1818 from prometheus/fabxc-1.0.0

*: cut 1.0.0

circle: add tag v-prefix

Merge pull request prometheus#1742 from prometheus/fabxc-0.20.0

*: cut 0.20.0

Merge pull request prometheus#1737 from prometheus/fabxc-0.19.3

Bump version to 0.19.3

Merge pull request prometheus#1688 from prometheus/beorn7/0.19

Cut 0.19.2

*: add 0.19.1 changelog

*: add 0.19.0 changelog

Update changelog for 0.18.0