Modified imgurRepoSync.sh to fix imgur link format change

The in-page imgur image links the script uses appear to have changed from 

<a href="http://i.imgur.com/[IMAGE]...

to

<a href="//i.imgur.com/[IMAGE]...

I changed the grep so it matches the new(?) format, and added a sed line to add the "http:" in front.

Works now as of 06 Oct 2013.