Add deploy locking and unlocking

[fool]

Customer Robert contributed this code to do this.

// Restore an old deploy. Sets the deploy as the active deploy for a site

func (deploy *Deploy) Unlock() (*Response, error) {

return deploy.client.Request("POST", path.Join(deploy.apiPath(), "unlock"), nil, deploy)

}

// Restore an old deploy. Sets the deploy as the active deploy for a site

func (deploy *Deploy) Lock() (*Response, error) {

return deploy.client.Request("POST", path.Join(deploy.apiPath(), "lock"), nil, deploy)

}