Replace "Flickr" with "Imgur"

In several Error-Messages the Image-Source was still stated as "Flickr"
instead of "Imgur". This was corrected.
Added Failure Timer

If loading from Twitter Api fails and the $.getJSON Error-Handling
fails too, a timeout timer reveals the error message.
If the error message is already shown when the succes function is
called, it will be hidden again.
Merge pull request #7 from zomtec/master

Added Failure Timeout for Twitter JSONP Request, replaced "Flickr" strings with "Imgur"