Merge pull request #2 from mmollaverdi/master

Added tests for validation of empty first and last name
Added missing Expr argument to show function
Merge pull request #3 from mmollaverdi/master

Added missing Expr argument to show function
Covariant Maybe
Merge branch 'master' into my_answers

Conflicts:
	src/main/scala/com/rea/adt/ExpressionProblemExercises.scala
	src/main/scala/com/rea/typesafety/OptionExercises.scala