Cleanup README

Images definitely work without it: http://daringfireball.net/projects/markdown/syntax#img.  I removed it because it was showing up in the header text where it looked a little odd.  The trailing `#` is related to the opening `#` for header syntax: http://daringfireball.net/projects/markdown/syntax#header.  It's optional and could be removed, but it doesn't get added to the result like the one in the middle did.