Control whether metadata merge conflicts result in a warning, an error, or nothing (only in vstack for now)
Improved description for ``metadata_conflicts`` and add the option to ``hstack`` and ``join``.
Ensure that an exception is raised if metadata_conflict is not one of e expected values.
Fixed typo
Use custom warning class
Always pick the right key
Added tests for metadata merging with hstack, vstack, and join
Started working on also providing control over metadata conflict errors/warnings for column metadata
For merging unit, format, and description metadata, always pick the last one
Extend metadata conflict control to column attributes (unit, format, description) and improve consistency.
Added documentation for conflict resolution of metadata
Added entries in CHANGES.rst
Whitespace
Fix typo
Merge pull request #1343 from astrofrog/metadata-conflict-control

Make meta-data merging emit warnings rather than raise exceptions by default