Update version 0.9.10 -> 0.9.11
Update version 0.9.10 -> 0.9.11

Changes
-------
* Deprecated `SampleSet.append_variables`

New Features
------------
* `append_variables` function, replacing the funcionality of `SampleSet.append_variables`
* `append_vectors` function, to add more data vactors to a sample set
* Documentation improvements
* Support for python 3.9

Fixes
------
* Fix c++ target for windows build
dwavesystems/dimod,dwavesystems/dimod