'Constructs a versioned url for the given path.
This method may be overridden in subclasses (but note that it
is a class method rather than an instance method).  Subclasses
are only required to implement the signature
``make_static_url(cls, settings, path)``; other keyword
arguments may be passed through `~RequestHandler.static_url`
but are not standard.
``settings`` is the `Application.settings` dictionary.  ``path``
is the static path being requested.  The url returned should be
relative to the current host.
``include_version`` determines whether the generated URL should
include the query string containing the version hash of the
file corresponding to the given ``path``.'

@classmethod
def make_static_url(cls, settings, path, include_version=True):

    url = (settings.get('static_url_prefix', '/static/') + path)
    if (not include_version):
        return url
    version_hash = cls.get_version(settings, path)
    if (not version_hash):
        return url
    return ('%s?v=%s' % (url, version_hash))
