Bump version 0.5.2 to 0.5.3. (ray-project#2936)

Bump version number to 0.5.2. (ray-project#2765)

Bump version to 0.5.1. (ray-project#2755)

Bump version to 0.5.0. (ray-project#2351)

Bump version to 0.4.0. (ray-project#1745)

Bump version to 0.3.1. (ray-project#1397)

Bump version number to 0.3.0. (ray-project#1247)

update version to 0.2.2 (ray-project#1178)

Bump version number to 0.2.1. (ray-project#1026)

Bump version to 0.2.0. (ray-project#877)