fix bug where twitter widgets weren't loading

See Twitter's [Embedded Timelines -> Overriding Timeline Selection](https://dev.twitter.com/web/embedded-timelines#timeline-selection) docs. Basically, we just set the `data-screen-name` param to either what was given in [council-info repo's people.js](https://github.com/techieshark/council-info/blob/gh-pages/people.js) file or to a default.

If you try this, currently, the Mayor's twitter feed should work and the Manager's feed says there haven't been any tweets (which is true currently).