Algorithms working when they shouldn't

[foobacca]

At commit c23fb3c it appears that the tests for leximin, maximin and nash are working - but they shouldn't.

In particular, the test is asking for 22 people but the categories data for geo_bucket is asking for a minimum of 3 people in each of the 8 geo_bucket values - so that is a minimum of 24 people.

So the selection should fail. But it passes. Need to investigate more.

[foobacca]

Note to self. Maybe the min_flex value allows this. Set it to same as min and see what behaviour we get.

[foobacca]

Add test cases for invalid targets.

Find out what the flex values are and document

More category set up tests