fix(alerts): Remove extra margin on the alert
fix(alerts): Remove extra margin on the alert

When the close button is followed by a media component, the margin
should be cleared. There is a special rule that handled this for alerts
inside a table which is how it is shown in the styleguide.

pivotal-cf/pivotal-ui,CanopyCloud/pivotal-ui,pivotal-cf/pivotal-ui,sjolicoeur/pivotal-ui,npm/pivotal-ui,npm/pivotal-ui,sjolicoeur/pivotal-ui,CanopyCloud/pivotal-ui,CanopyCloud/pivotal-ui,sjolicoeur/pivotal-ui,pivotal-cf/pivotal-ui,npm/pivotal-ui,sjolicoeur/pivotal-ui