Release v0.4.0

• add inspect command to check metadata disk usage and number of keys
• add retrieve command to retrieve an object
• add check command to check the integrity of an object
• server command to start the s3-cas server

v0.3.0

fix missed persist

v0.2.0

write object for meta

v0.1.1

fix `asm` feature flag and remove `binary` feature flag

v0.1.0

Add the fact that we only support 1 key

Signed-off-by: Lee Smet <lee.smet@hotmail.com>