Layout responsive events list and event details pages

As part of #138 two new pages are being added to laddr:
- Browse Events: http://laddr-v2-dev.poplar.phl.io/events
- Event Details
- Upcoming event we'll be promoting: http://laddr-v2-dev.poplar.phl.io/events/city-as-a-service-2016
- Recent event with full schedule input: http://laddr-v2-dev.poplar.phl.io/events/sustainability-2015

Here's a fully-featured event on the old site we're deprecating: Almost fully-features event page from past hackathon on the appsforphilly site we're deprecating: http://appsforphilly.org/events/transportation-2015

The most immediate use case will be using the direct link to the upcoming hackathon for promoting it. Key elements include:
- Prominent date, location
- Long markdown content area with multiple headlined main sections
- Detailed one-day or multi-day schedule
- Small list of subpages with detailed information about the event
- Gallery of sponsor logos
- Idea board or preview with link to full idea board page
- Gallery of RSVPd attendees
- List of links to projects founded for the event

If it sounds like a party flyer, it kind of is... but maybe could be less so

まず Browse Events と Event Details の URL を確認し、次に非推奨となった appsforphilly.org のイベントページと比較します。Issue に記載された主要なイベント情報、コンテンツ、スケジュール、サブページ、スポンサーのロゴ、参加者、アイデア、プロジェクトリンクを網羅するレスポンシブなイベント一覧ページと詳細ページが完成すれば、完了です。

索引モデルが issue の本文から書いたものです。