Merge pull request #19 from guangmingyao/yao_dev

Yao dev
Added two questions about integration by parts in the laplace transform section.
Merge pull request #20 from guangmingyao/yao_dev

made changes on week 1 note1--note3
Added more info on topics in the class and added one more example for the first day.
Merge pull request #42 from KellyBlack/black_dev

Black dev