more tests and a few tips
improved the introduction to the exercises
simplified eeeeverything in GroceryShopping
tests for parseIngredient
removed unused type alias
more hints for parseIngredient
Merge pull request #4 from tobiasgwaaler/lessonc-tobias

Lesson C, Tobias
Merge branch 'master' into vigenere
Added CreditCardNumberValidatorTests to main test file