Supports yum --enablerepo option (supports only base,updates for now)

[kotakanbe]

If you define as below in config.toml.

[servers.cent6]
host     = "127.0.0.1"
port     = "20062"
user     = "vuls"
keyPath  = "/path/to/id_rsa"
enablerepo = "updates,base"

Vuls issues yum with --enablerepo option

• yum check-update

yum --color=never --enablerepo=updates,base check-update

• yum --changelog update

yum  --enablerepo=updates,base --changelog update wget

See #246

For now, base and updates repository are supported.
Because a change-log format of additional yum repository is different for each repos...