Merge pull request #19 from guangmingyao/yao_dev

Yao dev
Added two questions about integration by parts in the laplace transform section.
made changes on week 1 note1--note3
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
Added a simple circuit diagram for a resistor.
Minor word changes and the addition of a circuit diagram.
Merge pull request #43 from KellyBlack/black_dev

Minor wording changes for the first lecture and a new image.
marked some texts in color, changed the date
change a typo on page 6
Merge pull request #21 from guangmingyao/yao_dev

Yao dev