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

Commencez par examiner les URL de Browse Events et Event Details, puis comparez-les avec la page d’événement obsolète de appsforphilly.org. Le travail est considéré comme terminé lorsque des pages responsives de liste et de détail des événements couvrent les informations importantes sur les événements, le contenu, les plannings, les sous-pages, les logos des sponsors, les participants, les idées et les liens vers les projets décrits dans l’issue.

Rédigé par le modèle d'indexation à partir du texte de l'issue.