Implement additional exercises

[BNAndras]

I'm planning on adding these practice exercises.

• [ ] Custom Set
• [ ] Rotational Cipher
• [ ] Sublist
• [ ] Transpose
• [x] Allergies
• [x] Bank Account
• [x] Circular Buffer
• [x] Proverb
• [x] Robot Simulator

[BNAndras]

Allergies will be next followed by Custom Set