added some more tests
fixed the animals weight
added get_gestation_period method
added get_gestation_perion test
added _mate_animals method
added _mate_animals() tests
added save and load methods
added unittests for the save and load methods
animals species database
some minor change
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deleted a comma :D
.
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changed '"' to ''' :D

- also changed the death chance
added script to run all tests at once
Merge pull request #1 from feralieva/peio

Peio