1.3.0

@ianna fixed class names in the documentation (PR #860).

@agoose77 fixed ak.is_none (PR #864).

@drahnreb made Parquet lazy-loading only build Forms for requested columns (PR #867).

@agoose77 and @drahnreb together made idioms like x["z"] = None work correctly by assigning a column of Nones (PR #880).

@jpivarski fixed some union-simplification issues in getitem-field (PR #870). Also fixed various bugs to enable Numba JIT-compiled functions to iterate over VirtualArrays created by lazy-reading Parquet (PR #871). Fixed a relic of the ptr().get() → data() transition for kernel interfaces (PR #877). Fixed some null-type issues with Arrow/Parquet columns (PR #878). And fixed matrix multiplication of a vector as an Awkward record (PR #868).