Merge pull request #62 from KellyBlack/black_dev

Updated the talk on determinants and vector space.
minor change on the note week8friday
Merge branch 'yao_dev' of github.com:guangmingyao/ODE-Recitation-Activities into yao_dev
Merge pull request #63 from KellyBlack/black_dev

Updated and reformatted the lecture on linear indepence.
conflict
conflict
Merge pull request #65 from KellyBlack/black_dev

Updated the introduction to systems of DEs
minor changes on wed note for week 9
fixed conflict
minor changes on solving systems
Merge pull request #37 from guangmingyao/yao_dev

Yao dev
Changed to color of some text
Merged Guangming's fixes.