Dascore 0.2.0

[d-chambers]

Just jotting down a few todos/ideas before DASCore's 0.2 release. This is mainly a personal brain dump.

• Coord support for strings
• Spool group columns that get passed to merging etc.
• coord groupby object? Spool groupby?
• Spool.put for adding contents.
• Big spool refactor
• array API support; patch function dispatch for array backends.
• add option for full_coords in FiberIO.scan; that way when complicated merges are requested the spool can lazily load the coords it needs.
  -coord hash function; include on summaries.
• Clean up deprecation