[WIP] Sponsors page

[pascaldevink]

Basic implementation of #4. The marquee was already made, but I wrote the behat scenario for it.
What's still left to do:

• Sponsor listing page
• Sponsor detail page
• Styling for both pages
• Better implementation of the sponsor slugs (perhaps by creating a more general translation or wrapper)
• Behat tests for the pages

What I don't know yet, is how to get to the sponsors listing from the homepage. For now, I made the sponsors header a link, but perhaps we should also make links to the detail page from the sponsors images in the marquee.

Also, if anybody has ideas for the styling and/or the implementation of the sponsor slugs (mostly, how to separate the functionality), please let me know 😅

[rdohms]

@pascaldevink one twist here.

The current implementation of the marquee only pulls in the sponsors from Meetup as a "quick fix". Our new solution should be standalone, and optionally push to Meetup. So feel free to drop all the current meetup integration and put in a new SponsorsBundle that handles all of that CRUD and etc.

[rdohms]

Finished in PR #64.