Dimod

Fixes
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* Support printing sample sets with discrete variables

New Features
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* New `DISCRETE` vartype for sample sets
* `DiscreteQuadraticModel` class
* New parallel constructor for dense c++ BQMs

New Features
------------
* New `DISCRETE` vartype for sample sets

New Features
------------
* `DiscreteQuadraticModel` class
* New parallel constructor for dense c++ BQMs

New Features
------------
* `Structured.to_networkx_graph` mixin method
* `.min`, `.max`, and `.sum` methods on BQM views
* `nonblocking_sample_method` decorators for asynchronous samplers
* `anti_crossing_loops`, `anti_crossing_clique`, and `doped` problem generators
* `BQM.to_file` and `BQM.from_file` methods for cyBQMs

Fixes
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* `VartypeView.relabel_variables` no longer sometimes returnes models with the wrong vartype
* `BQM.relabel_variables_as_integers` now works correctly when `inplace=False`

New Features
------------
* `BQM.normalize` now returns the value the BQM was scaled by
* `SampleSet.relabel_variables` no longer blocks for unresolved sample sets
* `FileView` has a new parameter, `ignore_variables` that treats the BQM as integer-labelled
* `ScaleComposite` no longer blocks

Fixes
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* `FileView.seek` now works correctly with `io.SEEK_END`

Changes
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* `BinaryPolynomial` support in `ScaleComposite` has been removed