New deployment payloads

We're going to be modifying the deployment payload webhook format to have a top-level key for deployment and deployment_status payloads. It's going to look this.

Proposed Deployment Payload Changes
===================================

DeploymentEvent paylods
-----------------------

#### Existing

```ruby
{
  :id          => @deployment.id,
  :sha         => @deployment.sha,
  :ref         => @deployment.ref,
  :task        => @deployment.task,
  :name        => @deployment.repository.name_with_owner,
  :environment => @deployment.environment,
  :payload     => @deployment.json_payload,
  :description => @deployment.description,
  :repository  => {…},
  :sender      => {…}
}
```

#### Proposed

```ruby
{
  :deployment  => {
    :url          => url(deployment_url),
    :id           => deployment.id,
    :sha          => deployment.sha,
    :ref          => deployment.ref,
    :task         => deployment.task,
    :payload      => deployment.json_payload,
    :environment  => deployment.environment,
    :description  => deployment.description,
    :creator      => user_hash(deployment.creator),
    :created_at   => time(deployment.created_at),
    :updated_at   => time(deployment.updated_at),
    :statuses_url => url("#{deployment_url}/statuses"),
    :repository_url => url(repository_url)
  },
  :repository  => {…},
  :sender      => {…}
```


DeploymentStatusEvent paylods
-----------------------

#### Existing

```ruby
{
  :id            => @deployment_status.id,
  :state         => state,
  :deployment    => deployment_hash(deployment), # Same as proposed format for deployment above
  :target_url    => target_url,
  :description   => description,
  :repository    => {…},
  :sender        => {…}
}
```

#### Proposed

```ruby
{
  :deployment_status  => {
    :url            => url(status_url),
    :id             => deployment_status.id,
    :state          => deployment_status.state,
    :creator        => user_hash(deployment_status.creator),
    :description    => deployment_status.description,
    :target_url     => deployment_status.target_url,
    :created_at     => time(deployment_status.created_at),
    :updated_at     => time(deployment_status.updated_at),
    :deployment_url => url(deployment_url),
    :repository_url => url(repository_url)
  },
  :deployment         => {…}, # Same as proposed above
  :repository         => {…},
  :sender             => {…}
}
```