Changed moxieplayer to pull poster variable instead of poster.jpg

Davit,

First, thanks for pushing this project out to github where I could fork and test.  I appreciate it very much.  Next, please have a look at the pull request here as I believe I found the issue with the poster not pulling and displaying properly.  I have been testing it now in my local setup and I am now seeing the expected poster rather than a 404 Not Found.

Thanks for the consideration,
Todd (aka coopster)

http://www.tinymce.com/forum/viewtopic.php?id=25429