Text based output format for bibid categories and date counts

[hornc]

Provide a text based output for exporting data.

Current code outputs:

Dates: [0, 1400, 1760, 1770, 1780, 1790, 1800, 1810, 1820, 1830, 1840, 1850, 1860, 1870, 1880, 1890, 1900, 1910, 1920, 1930, 1940, 1950, 1960, 1970, 1980, 1990, 2000, 2010] [34636, 0, 1, 1, 2, 5, 18, 22, 95, 146, 188, 325, 341, 462, 596, 828, 875, 956, 1294, 1666, 2456, 5346, 12925, 30085, 45280, 76277, 33109, 697]
No dates: 34636
No IDs: 294
Venn Categories: [294, 893, 351, 3362, 55381, 61284, 17013, 110054]

Needs something more usable.

• TSV for dates, for copy-paste into a spreadsheet?
• Venn categories; a format which can be passed directly back into matplotlib_venn or other Venn diagramming tools?

[hornc]

done in #5