append link to bad code when error type is SyntaxError

When we exec bad code and catch the exception then we have access to `backtrace` method of exception. This method return trace of bad code execution.

I found that when error type is SyntaxError — ruby not return link to bad code on `exception.backtrace` but link to bad code contain into exception message.

For test this case just put bad code (like `a = ` for example) into your application and see for result.

Here is what you should see ([screen](http://note.io/1dQx6FA)).

After patched the rails wrapper of exception, the application trace will be displayed correctly ([screen](http://note.io/1dQxe80)).