made language for test_questionfunctions_2a and 2b more clear
got rid of str+int issue in ch04_square
removed exercise header (because there are no exercises)
made last two questions func-12 and 14 get compiled
fixed test_functions_2_4
removed test_questionfunctions_2_1 because it was not covered in the chapter
changed prints to not print out a tuple
Revert "removed test_questionfunctions_2_1 because it was not covered in the chapter"

This reverts commit 2aeec302e09ae1917a14f5ead17b0b9f87dfec79.
added explanation that return ends function execution