Use a more efficient regex match

Hi,

When i set the Video Embed field to enable Vidyard, I am noticing that the first two characters after share/** are stripped. This is causing the video not to render.

Replication steps:

1. Add Video Embed field to basic page content type
2. Under Manage Display set format to video
3. Add Content-->Basic Page-->Enter "http://play.vidyard.com/share/MI_gb2lRkMzODtZq8dLE8Q" into Embed Video field
4. view page
5. observe that everything after MI is stripped

If I inspect the page and insert the part that was stripped, then the video displays properly.