Preserve syntax error line and column numbers when available

Modern versions of CoffeeScript include line and column numbers with syntax errors. However due to how ExecJS serializes exceptions, this metadata is lost – only the exception message is returned.

This pull request uses a wrapper function to include the line and column information in the exception message, preserving it for programmers who might otherwise be pulling their hair out.

I'd just remove the leading `:`. The separator makes sense when its coming after a filename.