fix muscl once again -- using SSP RK2
fix cfl condition
Final edits MUSCL notebook. Add ref to Shu & Osher.
Merge pull request #99 from numerical-mooc/muscl

MUSCL scheme, fixes RK2 and adds more explanation
Add README to folder for Module 1
file name
Add lesson summary
Add badge criteria, Module 1
typos
add optional evidence
Create README.md file
Add list of lessons
Update README.md
Add badge criteria
Update README.md
Add soft criterion on self-study of lessons
Update README.md
Update README.md
Add link to folder, Module 1
Add sof