initial commit - ftcs explicit heat transfer in 2d
initial crack at implicit method
initial commit -- proof of concept crank nicolson 1d heat solver
add speed comparisons to difference implicit options
lesson 3: write intro paragraphs
Add reference to van Leer, 1979
Write text on conservative discretization
Added intro to implicit scheme
Added style and small edits to notebook 1, module 4
add section on boundary conditions (unfinished)
clear output, change u->T and minor language tweaks
tweak language and segue from explicit to implicit
Add intro to Godunov method. Still needs work.

The explanation of Godunov's method is confusing and the figure is
wrong. More work to do  here.
add stencil and equation figures
add stencil for implicit schemes and continue working on implicit writeup
add figure for implicit formulas
add richtmyer stencil
Reorganize text on Godunov. Still needs work.
Add figure shock tube & Riemann
Embed figure and add more on Godunov