Created a button to remove attachment from thread

Earlier there was no button/link to remove an attachment. So if you
inserted an attachment you have to refresh the page to remove it

Fixes #36
Corrected WP coding standard
Escaping attachment URL and filename
Making attachement remove link red in color
Escaping attachment ID before insertion in DOM
Merge pull request #131 from VarunAgw/attachments

Add link to remove an attachment from a thread.