Merge pull request #2 from guangmingyao/black_dev

Black dev
Merge pull request #4 from guangmingyao/yao_dev

Yao dev
Merge pull request #6 from guangmingyao/master

units in double tank problem is changed to gram, rate out for tank 2 is changed to 4 l/min
Merge pull request #10 from guangmingyao/yao_dev

Yao dev
Bring master branch current to 2013.
Merge pull request #39 from KellyBlack/master

This is to bring the mast branch current to the final 2012 notes. This will allow us to make changes focused on 2013 for the dev branches.
Merge branch 'black_dev' of https://github.com/KellyBlack/ODE-Recitation-Activities
change the forcing term in linearModeling.tex, it was not possible for students to integrate
Merge branch 'master' of github.com:guangmingyao/ODE-Recitation-Activities
Merge branch 'master' into yao_dev