Travis: remove migration checking with Pydata tests, change logic
Travis: remove migration checking with Pydata tests, change logic

Logic for migration checking was reversed.

PyData application injects some changes, that result in a required
migration. This commit removes the migration checking from PyData test
matrix entry because it's pointless.

pbanaszkiewicz/amy,pbanaszkiewicz/amy,pbanaszkiewicz/amy,swcarpentry/amy,swcarpentry/amy,swcarpentry/amy