some initial implementation
added files
better development of state and evaluation
 more step metjhod work
improvements for state passing
made some dependencies more explicit; need to work out all vector updates
made readme
handles nth order derivatives but not updating dicts now
switching to more model centric view
added aux files
added trial exmaple
renaming
added back free variable class
added type info
bug fixes
now runs
added docstrings to a lot of things
added more docstrings and reorganized
docs
oops needed to add files