Use better pagination url, which is suggested by pelican default theme.

See https://github.com/getpelican/pelican/blob/master/pelican/themes/simple/templates/pagination.html as a reference.

This solution works better with custom **PAGINATION_PATTERNS** configuration (see [Using Pagination Patterns](http://docs.getpelican.com/en/3.3.0/settings.html#using-pagination-patterns) in pelican document).