Merge pull request prometheus#2937 from prometheus/cutbeta

Cut 2.0.0-beta.0

*: cut v2.0.0-alpha.3

*: cut v2.0.0-alpha.1

Bump version file

Bump version

Merge pull request prometheus#2706 from prometheus/cut162

Cut 1.6.2

Merge pull request prometheus#2705 from prometheus/cut153

cut 1.5.3