zarr 0.2.0

• Zarr version 2 stores can be read. Data types supported are those also included in the v.3 core specification. The compression codec has to be one of those supported by the v.3 core specification or zstd. Filters are not yet supported.
• HTTP stores can be read but only for Zarr v.3 and v.2 single-array stores and Zarr v.2 stores with consolidated metadata present in the root group of the Zarr store.
• Chunk key encoding from v.2 and "default" and "v2" from v.3 supported.
• The blosc package is now imported as it is the default compression codec.
• zstd compression codec added.
• Fixed reading integer64 data.