Added discussion on order of convergence of C-N
change from pickle to numpy.load for compatibility across python2.x and 3.x
Merge remote-tracking branch 'refs/remotes/origin/parabolic_dev' into parabolic_dev
update data file address for assessment
added comparison with 1st order in time method
Text edit, add video, links in references

Also, author list in alphabetical order.
Edit explanation of GS model

Removing use of "particles" and explaining more the reaction term.
Final edits to reaction-diffusion notebook
Edit text and other tweaks of Crank-Nicolson lesson

Split some cells, tweaked overflowing equations, authors in
alphabetical order, changed "ftcs" for "btcs" in some functions.
run all on notebooks 5 and 6.  add reference to aliensaint for RD parameters
Merge branch 'master' into parabolic_dev

Conflicts:
	lessons/04_spreadout/05_Crank-Nicolson.ipynb
	lessons/04_spreadout/06_Reaction_Diffusion.ipynb
Merge branch 'parabolic_dev'