Mthree

- Adds `Collection` classes for easily working on collections of distributions in a similar manner to a single distribution.
- Adds the ability to pass `expval` functions a string of operators, eg. `'IZZZIZII'`, that indicate which diagonal operator is assumed to act on the given qubits.
- Adds tutorials section to documentation.
- Adds new basic VQE tutorial to show how one can use mitigation in a simple iterative algorithm.

Micro release to fix docs issues and push out wheels.

Releasing to verify wheels uploads and docs builds all work as expected.

- Added a new `balanced` calibration method of 2N circuits. It is now the default.

- Added `final_measurement_mapping` routine for use with transpiled circuits.

- First release that uses auto-release tools from mtreinish.

- Ability to pass list of counts to `apply_correction`.
- Fixes for loading calibrations from files.