Prepare 2.0-alpha-1 release

Prepare 1.6.3 release

Prepare 1.6.2 release

Prepare 1.6.1 release

Prepare 1.6 release

Merge pull request square#871 from square/one-five-foh

Prepare 1.5.4 release

Merge pull request square#859 from square/one-five-three

Prepare 1.5.3 release

Merge pull request square#814 from square/1.5.2

Prepare 1.5.2 release

Prepare 1.5.1 release

Prepare 1.5 release