Added CFD Python files
Updates for numerical-mooc

    * Deleted and changed references to CFD Python
    * Added license
    * Changed style
    * Changed imports to agreed convention
Trivial missing full stops.

Some semicolons to suppress output near plots.
Changed more references to CFD Python
Added solutions to spacetime module
Merge branch 'master' into spacetime_solution (update stylesheet)
replace all 26314 with eqn envir. to enable numbering
Merge pull request #8 from numerical-mooc/spacetime_solution_add_eqn_numbers

replace all $$ with eqn envir. to enable numbering
recreate shortcut for dt that keeps getting deleted
added section on Richardson extrapolation in 3rd lesson
Added discussion on Richardson extrapolation
explain we follow Milne-Thompson/ centrifugal force

Derivation uses theta as positive upwards, and forces are in a rotating
frame, so we should properly speak of centrifugal force
checking a sign, executed style, no changes
Add new figure of forces on the glider

With trajectory pointing up, for a positive angle
Rewrote full-model formulation

Without magically eating constants like in the math notes. The factors
have physical significance!
Went through first two modules
Added gitignore for files inside lessons
removed pyc file
added corrections
Correct minor typos and grammar points.