Csv-diff

- New `--show-unchanged` option for outputting the unchanged values of rows that had at least one change. 9
- Fix for bug with column names that contained a `.` character. 7
- Fix for error when no `--key` provided - thanks, MainHanzo. 3
- CSV delimiter sniffer now `;` delimited files. 6

- Support for TSV files. The tool will automatically detect if the input is CSV or TSV, or you can use the new `--format=tsv` or `--format=csv` options to over-ride the automatic detection. Thanks, Thomas Sibley for contributing this new feature. (4)

Tweaked output formatting of added/removed columns for better consistency with added/removed/changed rows.

Handle columns being added and removed

My [sf-tree-history project](https://github.com/simonw/sf-tree-history) unexpectedly broke because the columns in the CSV file changed.

https://circleci.com/gh/simonw/sf-tree-history/110

`csv-diff` can now detect and handle this without crashing.

Example commit: https://github.com/simonw/sf-tree-history/commit/781d7c4abf5d0022609a2b20cd3d5f5616826835

--singular` and `--plural` options, closes 2

Added and deleted rows now display in a more human-friendly format than raw JSON:

$ csv-diff one.csv two.csv --key=id
1 row changed, 1 row added, 1 row removed

1 row changed

Row 1
age: "4" => "5"

1 row added

id: 3
name: Bailey
age: 1

1 row removed

id: 2
name: Pancakes
age: 2


Example commit here: https://github.com/simonw/sf-tree-history/commit/184efa - compare with https://github.com/simonw/sf-tree-history/commit/dd08cc which demonstrates the previous behaviour.