Important Attributes
`email`	The email address of the customer who earned the new tier.
`customer`	The customer object who earned the new tier.
`new_tier`	Object describing the new tier they just earned.
`old_tier`	Object describing the tier they came from. Attribute won’t be present if they had no previous tier.

{
    "topic": "swell/tier/earned",
    "name": "Swell Tier Earned",
    "email": "john.smith@gmail.com",
    "customer": {
        "total_spend_cents": 0,
        "total_purchases": 0,
        "perks_redeemed": 2,
        "last_purchase_at": null,
        "email": "john.smith@gmail.com",
        "referred_by": "jane.smith@gmail.com",
        "points_earned": 375,
        "points_balance": 375,
        "points_expire_at": null,
        "first_name": null,
        "last_name": null,
        "last_seen_at": "2016-10-15T18:14:56.000Z",
        "third_party_id": "4302977345",
        "vip_tier_name": "SILVER",
        "vip_tier_ends_at": "2017-10-31",
        "referral_code": {
            "code": "x09u052",
            "shares": 0,
            "facebook_shares": 0,
            "twitter_shares": 0,
            "email_shares": 0,
            "emails_sent": 0,
            "emails_viewed": 0,
            "links_clicked_from_email": 0,
            "links_clicked_from_twitter": 0,
            "links_clicked_from_facebook": 0,
            "orders": 1,
            "amount_cents": 3000,
            "average_amount_cents": 3000,
            "expires_at": null,
            "expired": false,
            "completed_referral_customers": [{
                "email": "hillary.clinton@gmail.com",
                "first_name": "Hillary",
                "last_name": "Clinton",
                "referral_points_contributed": 0,
                "last_seen_at": "2016-10-15T16:38:20.000Z"
            }],
            "email": "john.smith@gmail.com",
            "unique_clicks": 1,
            "total_clicks": 1
        }
    },
    "new_tier": {
        "id": 2,
        "name": "GOLD",
        "description": "Earn Gold status after spending $100",
        "points_earned": 0,
        "amount_spent_cents": 10000,
        "purchases_made": 0,
        "points_multiplier": 1.50,
        "rank": 2
    },
    "old_tier": {
        "id": 1,
        "name": "SILVER",
        "description": "Earn Silver status after spending $50",
        "points_earned": 0,
        "amount_spent_cents": 5000,
        "purchases_made": 0,
        "points_multiplier": 1.20,
        "rank": 1
    }
}