Sleep for half a second at exit in order to avoid losing log messages… (

ray-project#4254)

Bump version from 0.6.2 to 0.6.3 (ray-project#3972)

Bump version (ray-project#3787)

bump version from 0.6.0 to 0.6.1 (ray-project#3610)

Bump version from 0.5.3 to 0.6.0. (ray-project#3420)

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)