Implement exercise food-chain

[luanjpb]

---

Fixes #750

[ilya-khadykin]

@LU4XLII could you please fix code style issues:

2.78s$ flake8
./exercises/food-chain/example.py:33:80: E501 line too long (80 > 79 characters)
./exercises/food-chain/food_chain_test.py:15:80: E501 line too long (92 > 79 characters)
./exercises/food-chain/food_chain_test.py:22:80: E501 line too long (92 > 79 characters)
./exercises/food-chain/food_chain_test.py:30:80: E501 line too long (92 > 79 characters)
./exercises/food-chain/food_chain_test.py:39:80: E501 line too long (92 > 79 characters)
./exercises/food-chain/food_chain_test.py:49:80: E501 line too long (92 > 79 characters)
./exercises/food-chain/food_chain_test.py:58:1: E302 expected 2 blank lines, found 1
./exercises/food-chain/food_chain_test.py:61:80: E501 line too long (82 > 79 characters)
./exercises/food-chain/food_chain_test.py:63:1: E305 expected 2 blank lines after class or function definition, found 1
The command "flake8" failed and exited with 1 during .

[luanjpb]

Fixed up

[ilya-khadykin]

Thanks for working on this

I've left a comment, please take a look

[ilya-khadykin]

Please implement other tests from https://github.com/exercism/problem-specifications/blob/master/exercises/food-chain/canonical-data.json

Could you also leave a comment stating what version of canonical-data.json the tests were adopted as discussed in #784 if applicable?
The format is:

# Tests adapted from `problem-specifications//canonical-data.json` @ v1.0.0

[luanjpb]

Ok I'll work on this now.

[luanjpb]

All tests implemented

[ilya-khadykin]

Thanks for working on this, @LU4XLII 🏆