Add CFL condition figure
Embed CFL figure and make text more precise
LaTeX typo
fix typo in jsanimation explanation text
Add four stencil figures
Started 1st notebook of 3rd module

    * Added CFDPython's Burgers' lesson to use as a base
typo fix
Modified notebook 1 of module 3

    * Added welcome message
    * Added discussion on conservative schemes
    * Added derivation of traffic model
    * Changed all references to Burgers' equation to traffic model in Lax-F, L-W (only text) and Mac
    * Need to check L-W derivation
    * Having trouble with MacCormack (doesn't update)
    * Haven't touched B-W
cubic flux version
solve for cubic flux equation using sympy
Worked on first notebook, module 3

    * Added discussion on wave speed
    * Added discussion on stability of backward difference
    * Added example with upwind
    * Added discussion on CFL for nonlinear waves
Merge remote-tracking branch 'refs/remotes/origin/wave_dev' into wave_dev
add derivation of cubic traffic flux
rename cubic notebook
Edits on notebooks 1 and 2 of module 3

    * Separated into two notebooks
    * Removed upwind from first notebook
Edits on convection schemes notebook

    * Removed upwind
    * Modified Lax-F and Lax-W to the "red light" example
    * Edited Lax-W derivation to traffic model
    * Edited mistakes in Lax-W derivation
    * Added stencil and square wave figures from PASI lessons
Edits on convection schemes notebook

    * Added discussion on reversed MacCormack
    * Added Dig Deeper section:
        * Explains why we introduce new methods
        * Discusses shock velocity
    * Changed references to CFL to \Delta t/\Delta x
finish calculation of new flux function
Merge branch 'wave_dev' of https://github.com/numerical-mooc/numerical-mooc into wave_dev
first pass language edits