Fixed an error condition in bitlify: if a string is passed to it and there is a problem, return the string unaltered

Our desired behavior:  Pass a full complete canonical URL of type string to bitlify in a template and get a shortened URL.

Before this checkin, this works EXCEPT in the case of http://localhost[:xxxx]/.  The main bit.ly site won’t shorten it (returns an INVALID_URI error).  This fails which causes an exception it django-bitly the throw an error.  The templatetag bitly wrapper catches the error and tries to call .get_absolute_url() on the passed in object.  But the passed in object is a string, and does not have this parameter.  So the attempt to call the invalid method generates another execption, whtich causes the entire template to fail rendering.

This is a small patch fix for our purposes.  AFAICT, there is a quirk in the framework where passed in strings (instead of objects) aren't handled consistently.  This would ideally be fixed on a deeper level.  Add to "Someday Maybe" list.
Specifically check for localhost as part of the full URL, and if so throw an exception because bitly does not shorten localhost URLs.
Merge pull request #1 from Everpath/localhost_update

Update bitty to handle URLs on localhost