fix twitter stream embedding for event pages

[bridgetkromhout]

While we have a working twitter feed for the main page, it's built into the layout (https://github.com/devopsdays/devopsdays-web/blob/master/themes/devopsdays-legacy/layouts/partials/twitterfeed.html).

It would be nice to allow events to embed their own twitter feeds - do they need a customized layout to do that? DC's doesn't work when imported with the exact code that worked for webby. See http://devopsdays.github.io/events/2016-washington-dc/contact/ versus what's in the code:

https://github.com/devopsdays/devopsdays-web/blame/master/content/events/2016-washington-dc/contact.md#L12-L13

[bridgetkromhout]

Heads up to @nathenharvey that DC's twitter feed on the contact page isn't working right now. (I've also still got sponsors to import after dinner.) Is the twitter feed a must-have for you before a cutover? Thanks.

[bridgetkromhout]

@nathenharvey says "Cutover without it. Sorry not logged into github from my phone. "

Note: it works on http://devopsdays.github.io/events/2016-oslo/welcome/ - compare and figure out what the difference is.

[bridgetkromhout]

Resolved in #296.