Awkward

Fixed `ak.unflatten` to include trailing `0` in its `counts` (in the structure on the left, if `axis != 0` or partitioned, at all otherwise): PR 743.

Implemented `row_groups` parameter of `ak.from_parquet`: PR 748.

Added methods: `ak.Array.to_list`, `ak.Record.to_list` (synonym for `tolist`), and `ak.Array.to_numpy`: PR 750.

NumPy scalars iterated over as numbers: PR 751.

Better error message for bad concatenation: PR 752.

Fixed `ak.num` on PartitionedArrays: PR 757.

drahnreb fixed several issues with categorical arrays and Arrow conversion: PR 727.

jpivarski updated `ak.unflatten` to have an `axis` parameter (PR 731), and to make it work on PartitionedArrays (732), added `ak.run_lengths` (733) and `ak.strings_astype` (734), and implemented `ak.argsort` for strings, fixing some issues with `ak.sort` for strings (736).

Significantly, the depth of arrays was changed to not count the inner dimension of strings: PR 736. Now an unnested array of strings has the same depth as an unnested array of integers: the dimension of the lists comprising the strings themselves doesn't count.

The fix that motivates this patch release is henryiii's repair of the SDist distribution: PR 720. The addition of dlpack wasn't included in the source distribution, so `pip install awkward` without an available wheel was failing due to not having all the headers it needed to compile.

Also fixed jagged slices: issue 723, PRs 725 and 729, as well as a segfault in `ak.flatten`: issue 724, PR 726.

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.