v0.24

Please note this release contains some backwards-incompatible changes:

• The functions petl.valuecounts() and petl.aggregate() have changed their behaviour slightly, such that the fields in the output table may be different from previous versions. If a single field is used as the key argument then that field name will be used instead of "key" in the output table header. If a compound key is used, all key fields will be output as separate fields.
• The variable petl.transform.defaultbuffersize has moved to petl.transform.sorts.defaultbuffersize.

Note also that the petl.transform package has been refactored to break what was a very large module up into smaller pieces. Similar work is planned for the petl.io module in a subsequent release.

A full list of all changes is available at https://github.com/alimanfoo/petl/issues?milestone=23&state=closed