Allow blank URLs in BatchRequest for object updates
Allow blank URLs in BatchRequest for object updates

Facebook allows object updates by making POST requests to a blank edge
ID and specifying scrape=true and an id (either an object instance id
or a URL) as parameters.  BatchRequest doesn't currently allow
relativeUrl to be blank.  Facebook doesn't support either "." or "./"
as relativeUrls.  "?" and "/" are workarounds, but they're confusing,
and they don't mirror Facebook's documentation.

See https://developers.facebook.com/docs/sharing/opengraph/using-objects#update

restfb/restfb