support project's events with v4

[lethe3000]

get project's event from v3 works fine

GET /api/v3/projects/{id}/events?action=pushed

but with v4 api response data is

[
    {
        "project_id": 622,
        "action_name": "deleted",
        "target_id": null,
        "target_type": null,
        "author_id": 156,
        "target_title": null,
        "created_at": "2018-04-25T02:05:16.361Z",
        "author": {
            "id": 156,
            "name": "xushiyi",
            "username": "xushiyi",
            "state": "active",
            "avatar_url": "https://www.gravatar.com/avatar/78cf85165bd711cd5fc63477cb6ba0dc?s=80&d=identicon",
            "web_url": "http://git.56qq.com/xushiyi"
        },
        "push_data": {
            "commit_count": 0,
            "action": "removed",
            "ref_type": "branch",
            "commit_from": "8ed326c8b2d33d8d61e3ef6ef1cc4ac02c322c4e",
            "commit_to": null,
            "ref": "v4",
            "commit_title": null
        },
        "author_username": "xushiyi"
    }
]

so api.models.Event cannot handle data in field "push_data"
could you please verify this, thank you

[gmessner]

@lethe3000
GitLab has added several fields to the event, "push_data" being one of them. I have updated the Event class and unit tests for all known v4 fields and released 4.8.15