add initial commit for exercise 12
add exercise 13 init commit
add exercise 15 py code and test.tx
test.tx is just a few words for ex15.py to parse
add exercise 17
add exercise 18 init commit
exercise 19
add exercise 20 init commit
add exercise 21 init commit
add exercise 26, a test!, init commit
fix various typos, need to commit more
add exercise 29 init commit
add many more ifs
fix ln 23 typo from % to 5
fix ln31, added : to start block