Upcoming events we are speaking and attending

This introduces two new sections at the bottom of the Events & Talks page:
- Upcoming events we are speaking at
- Upcoming events we are attending

It queries the "unofficial" Lanyrd api to collect event data for each user in the [`authors.json`](https://github.com/guardian/developers-site/blob/6f1364716a829316ef6b63fc03ce24c80d380fd0/src/content/authors.json#L6) file, then flattens the data and dedupes events multiple people are talking or attending.

Unfortunately the api does not support CORS or JSONP, therefore I am constructing the data on build of the site in the gupl file and not dynamically on page load. The alternatively would have been to create a simple proxy, but this method was preferred. It was agreed that setting up a scheduled build for the project in TeamCity every morning would prevent the data from going stale.

I have ran the design changes past @paulrobertlloyd but the [copy](https://github.com/guardian/developers-site/blob/6f1364716a829316ef6b63fc03ce24c80d380fd0/src/events-%26-talks.ejs#L96) underneath each section needs some love.

### Screenshot
![google chrome](https://cloud.githubusercontent.com/assets/80089/3638480/8b602f2a-104c-11e4-9b48-30d47cae6b9b.png)

You can use the `unset` mixin to unset.

I also prefer to be explicit about what I'm unsetting and where I'm unsetting it from: https://github.com/guardian/developers-site/blob/master/CONTRIBUTING.md#css