Merge pull request #18 from guangmingyao/yao_dev

Yao dev
Merge pull request #21 from guangmingyao/yao_dev

Yao dev
Merge pull request #24 from guangmingyao/yao_dev

Yao dev
Merge pull request #26 from guangmingyao/yao_dev

Yao dev
Merge pull request #28 from guangmingyao/yao_dev

Yao dev
Merge pull request #30 from guangmingyao/yao_dev

Yao dev
Merge remote-tracking branch 'origin/yao_dev' into black_dev
Merge pull request #32 from guangmingyao/yao_dev

Yao dev
Set up the main file to print out the notes for the day on linear models
Fixed the difference between branches
Added images for a single tanke problem
Added a new image for the first tank problem example.
Merge pull request #48 from KellyBlack/black_dev

Added a new image for the first tank problem and made a minor word changing for one Newton's Law of Cooling problem.