Update README.md

added week5 quiz answers

added week6 quiz answers

project 6, questions - completed

added week 6 source files

project 6, sentences - completed

project 5, traffic - completed

added quiz answers from weeks 2, 3, 4

project 4, nim completed

source files added

project 4, crossword - shopping completedd

project 3, crossword - completed

added week 3 source files

project 2, heredity - completed

project 2, pagerank - completed