Initial revision
many changes.  Now the grid and data parts are separate classes.  BCs
are now done on a per-variable basis.  This is set when we register the
variable.  The bc_test.py tests all the BC options.
add proposed directory structure
more details
add IO
runtime parameters functionality
structure
somre notes
add tree
warning / error
start of driver
more progress
basic structure working
more progress
reconstruction
more progress
advection works now (needed to fill BCs)
missing files
add list of exercises to promote
add 4th order and no limiting options.  Add visualization