Bringing github version of plugin into parity with WP.org plugin repository
Fixing PHP deprecated warning: eregi() is deprecated as of PHP 5.3.0
Use WordPress's HTTP API to get the Gist content, since that's built to be robust and handle many different server configs.
Adding in simplistic Gist ID validation
Since the Gist URL structure is the same throughout, only set it once and add to it as needed.
Add proper escaping when printing the URL to screen.
Sanitize the filename.
Update Gist ID parsing to account for usernames in the Gist.
Fixing off-by-one error in Gist username detection.
Changed to show error message if id is null.  Previously it would show an error if both id and file were null, but the error wouldn't output anything useful.
Removing unnecessary trim($file), sanitize_file_name() handles this for us.
Fixing typo in search engine fallback url
Changing ?> to //EOF so nobody has to worry about whitespace after the closing ?>
Bumping "Requires at least" and "Tested up to"