Use timestamp from server for partial update

[StoneFrog]

Changes that should solve #29 . As mentioned in discussion, it will require timestamp to be returned in API response. To preserve integrity, MissingTimestapError is raised if there is no request_timestampinside meta.

[Mandaryn]

so bookingsync-api client from version 0.1.3 should have another property pagination_first_response, this should be used instead of last_response to get the proper timestamps of the first paginated request, to properly set the timestamps