Awkward

New patch release motivated by a bug discovered in Uproot's tests: PR 719. (From now on, Uproot will test Awkward release candidates.)

Also, 717 adds an optional `behavior` argument to every function that takes a `highlevel=True/False`.

Also from now on, only critical bug-fixes (like this one) will be patch releases and other updates will all go into release candidates for the next non-patch release (e.g. 1.2.0, [scheduled for 2021-04-01](https://github.com/scikit-hep/awkward-1.0#roadmap)).

This is the February 2021 release (see Roadmap).

No change with respect to 1.1.0r5.

Hopefully the last prerelease before 1.1.0.

Updates to Arrow 3.0. PR 709.

`getitem_field` calls `simplify_optiontype`. PR 714.

Minor changes, but one is a feature, not a bug-fix, so it needs to be pre-released before 1.1.0. I need to get 1.1.0 out soon, but I want the Parquet stuff to be in it.

Can now read and write Parquet datasets (conventions for sets of multiple files): PR 706, fixes 368 (old!).

Also, Python 2 can use ellipsis because we have pybind11 2.6 now: PR 707, fixes 705.

More minor bug fixes, mostly related to partitioned arrays and Parquet files: PRs 703 and 699.

Actually remove the features that have been deprecated, [scheduled to be removed in 1.1.0](https://github.com/scikit-hep/awkward-1.0#roadmap): PR 698.

Fixed 689, the dimension of arrays returned by empty slices: PR 691.

ianna fixed tuple-building in ArrayBuilder to guard against specifying a nonexistent slot and segfaulting: 697.

Various fixes in preparation for a SciPy 2021 tutorial:

* Added [ak.materialized](https://awkward-array.readthedocs.io/en/latest/_auto/ak.materialized.html) to force-materialize arrays (opposite of [ak.virtual](https://awkward-array.readthedocs.io/en/latest/_auto/ak.virtual.html)) because debugging very lazy deferments is hard.
* Can now use `np.newaxis` to give one array the same number of dimensions as another for slicing (which closes 492).
* Fixed `ak.min`/`ak.max` with `axis != None` for partitioned data.
* Fixed a bug that affected boolean-masking of partitioned data.